I have written several articles the environment. A list of links have been provided at bottom of this article for your convenience. This article will, however address different aspects on the environment and the planet in general.
Table of Contents
-What is Evolution
-What is Natural Selection
-What have genes got to do with it?
-Different Types of Evolution
-Are humans Still Evolving?
-A catalogue of human genetic variation
-What is Inheritance?
-How is genetic material inherited
-How is sex determined?
-What is Mendelian Inheritance?
-What is genetic variation?
-Record-breaking simulation hints at how climate shaped human migration
-Why curly hair was an evolutionary advantage
-If alien life exists in our solar system, it may look like this
What is evolution?
In biology, evolution is the change in the characteristics of a species over several generations and relies on the process of natural selection.
- The theory of evolution is based on the idea that all species are related and gradually change over time.
- Evolution relies on there being genetic variation in a population which affects the physical characteristics (phenotype) of an organism.
- Some of these characteristics may give the individual an advantage over other individuals which they can then pass on to their offspring.
What is natural selection?
- Charles Darwin’s theory of evolution states that evolution happens by natural selection.
- Individuals in a species show variation in physical characteristics. This variation is because of differences in their genes.
- Individuals with characteristics best suited to their environment are more likely to survive, finding food, avoiding predators and resisting disease. These individuals are more likely to reproduce and pass their genes on to their children.
- Individuals that are poorly adapted to their environment are less likely to survive and reproduce. Therefore their genes are less likely to be passed on to the next generation.
- As a consequence those individuals most suited to their environment survive and, given enough time, the species will gradually evolve.
Natural selection in action: the Peppered moth
- Before the industrial revolution in the mid-1700s, the peppered moth was most commonly a pale whitish colour with black spots.
- This colouring enabled them to hide from potential predators on trees with pale-coloured bark, such as birch trees.
- The rarer dark-coloured peppered moths were easily seen against the pale bark of trees and therefore more easily seen by predators.
- As the Industrial Revolution reached its peak, the air in industrial areas became full of soot. This stained trees and buildings black.
- As a result, the lighter moths became much easier to spot than the darker ones, making them vulnerable to being eaten by birds.
- The darker moths were now camouflaged against the soot-stained trees and therefore less likely to be eaten.
- Over time this change in the environment led to the darker moths becoming more common and the pale moths rarer.
What have genes got to do with it?
- The mechanisms of evolution operate at the genomic level. Changes in DNA sequences affect the composition and expression of our genes, the basic units of inheritance.
- To understand how different species have evolved we have to look at the DNA sequences in their genomes.
- Our evolutionary history is written into our genome. The human genome looks the way it does because of all the genetic changes that affected our ancestors.
- When DNA and genes in different species look very similar, this is usually taken as evidence of them sharing ancestors.
- For example, humans and the fruit fly, Drosophila melanogaster, share much of their DNA. 75 per cent of genes that cause diseases in humans are also found in the fruit fly.
- DNA accumulates changes over time. Some of these changes can be beneficial, and provide a selective advantage for an organism.
- Other changes may be harmful if they affect an important, everyday function. As a result some genes do not change much. They are said to be conserved.
Different types of evolution
- When the same adaptations evolve independently, under similar selection pressures.
- For example, flying insects, birds and bats have all evolved the ability to fly, but independently of each other.
- When two species or groups of species have evolved alongside each other where one adapts to changes in the other.
- For example, flowering plants and pollinating insects such as bees.
- When a species splits into a number of new forms when a change in the environment makes new resources available or creates new environmental challenges.
- For example, finches on the Galapagos Islands have developed different shaped beaks to take advantage of the different kinds of food available on different islands.
Sketches of the heads of finches from the Galapagos Islands showing the differences in their beak shapes due to evolution.
Are humans still evolving?
For much of nature, natural selection and ‘survival of the fittest’ still play a dominant role; only the strongest can survive in the wild. As little as a few hundred years ago, the same was true for humans, but what about now?
Nowadays, with the availability of better healthcare, food, heating and hygiene the number of ‘hazards’ we experience in our lives has dramatically reduced. In scientific terms, these hazards are referred to as selection pressures. They put pressure on us to adapt in order to survive the environment we are in and reproduce. It is selection pressure that drives natural selection (‘survival of the fittest’) and it is how we evolved into the species we are today.
The question is, now we have fewer selection pressures and more help in the form of medicine and science, will evolution stop altogether for humans? Has it stopped already?
Genetic studies have demonstrated that humans are still evolving. To investigate which genes are undergoing natural selection, researchers looked into the data produced by the International HapMap Project and the 1000 Genomes Project.
A catalogue of human genetic variation
The International HapMap and 1000 Genomes Projects both aimed to catalogue genetic variation in DNA samples taken from individual humans from across the world.
The majority of the catalogued human variation is characterised by single base changes, referred to as single nucleotide polymorphisms (SNPs). The location and frequency of these changes allows us to provide a list of regions in the human genome where genetic variation is common. Patterns of reduced variation help scientists to identify genes that may have recently been positively selected for by natural selection.
How are genetic variants found?
Genetic variants can be found by comparing the genomes of different people and looking to see where there are differences in the DNA sequence and where the genes are located in their genomes. When genetic variants confer a particular advantage and improve our fitness they are more likely to survive and be passed onto future generations, thus becoming more common in a population. When this happens, a pattern or ‘signature’ can be found in the genomes of the population. This is because, as a genetic variant starts to spread through a population, it doesn’t come alone but brings with it some nearby genetic ‘passengers’. These passengers are bits of DNA that are located on either side of the advantageous variant. So, if scientists find this signature in lots of genomes in a population, it is one of the first signs that natural selection could be operating. It suggests that they all stem from a common ancestor and have therefore inherited the same pattern of genetic variation.
If the genomes of two populations are found to be very different, it could be a sign that selection has occurred in one population, but not the other. As the advantageous gene starts to become more common, it can influence which other genes are expressed and even reduce the overall level of genetic variation in the surrounding area of the genome, making it stand out.
Unfortunately, even in the absence of selection, any of these patterns can turn up by chance, especially when the whole genome is examined. To make things more complicated, events such as population expansion can mimic some of the same effects. There is no perfect way to recognise where selection has occurred, but we sometimes get a very strong hint.
Scientists have found that the majority of genes that have undergone recent evolution are associated with smell, reproduction, brain development, skin pigmentation and immunity against pathogens.
One example of recent natural selection in humans involves the ability to tolerate the sugar, lactose, in milk. In most parts of the world, adults are unable to drink milk because their body switches off the intestinal production of lactase, an enzyme that digests the sugar in the milk, after weaning. As these people cannot digest the lactose sugar they suffer symptoms including bloating, abdominal cramps, flatulence, diarrhoea, nausea, or vomiting.
Yet, more than 70 per cent of European adults can quite happily drink milk. This is because they carry a regulatory change in the region of DNA that controls the expression of the gene that codes for lactase. This DNA change enables the lactase gene to be switched on and lactase production to continue, even after weaning. This genetic change appears to have happened between 5,000 and 10,000 years ago, which is around the same time domestication of milk-producing farm animals, such as cows, was established in Europe.
This suggests that being able to drink milk into adulthood provided a strong evolutionary advantage in Europe. This may be because sun exposure was much lower in Europe and people were in greater need of the vitamin D found in cow’s milk. Or it may be because cow’s milk provides a much safer and cleaner alternative to drinking water that may cause disease. Milk may also have prevented death from starvation when crops failed and food was scarce. Those who could not tolerate lactose would die of starvation, while those who could tolerate lactose would survive.
Whatever the reason, a strong selection pressure must have favoured those people whose lactase gene remained switched on. This variant of the lactase gene is so common in Europeans that we now consider lactose intolerance to be a health condition, rather than the natural process that it is.
The strongest evolutionary pressure of all comes from infectious diseases. Millions of people die from infectious diseases each year, particularly in the poorer regions of the world. People who are able to survive infections are more likely to pass on their genes to their offspring. However, genes that provide an advantage against one disease may not provide an advantage when faced with another.
The Caspase-12 gene
When infectious diseases became more common in human populations, perhaps because populations grew in size and pathogens were able to spread more rapidly, people with a genetic advantage were more likely to survive and reproduce. As a result, these genetic advantages were selected for, allowing more people to survive and fight disease. In some cases, a genetic advantage resulted from losing the full activity of a gene.
A good example of this is the caspase-12 gene. Caspase-12 works as a part of our immune system, responding specifically to bacterial infection.
In a study carried out by researchers at the Wellcome Trust Sanger Institute in 2005, it was suggested that the caspase-12 gene was gradually inactivated in the human population because the active gene can result in a poorer response to bacterial infection. People with fully functional caspase-12 were at a much higher risk of a fatal bacterial infection (sepsis) if bacteria entered the bloodstream, than people with the inactive version of the gene.
Before improved hygiene and antibiotics, survival of severe sepsis would have been a strong selective force for the inactive gene, which would have been greatly favoured. Today, people with two copies of the inactive gene are eight times more likely to escape severe sepsis if suffering with an infectious disease and three times more likely to survive.
But the study leaves us with a key question. If it is so good to have the inactive gene, why did our ancestors have an active form in the first place? It may be because in some areas of the world having the active gene carries an equal advantage to carrying the inactive gene in other areas of the world. What is clear however, is that all organisms are dynamic and will continue to adapt to their unique environments to continue being successful. In short, we are still evolving.
HIV is a modern-day driving force for human evolution. In certain parts of South Africa, nearly half of women are infected with the virus. In a study in Durban, Dr Philip Goulder and colleagues from the University of Oxford found that women with a certain combination of variants in a human leukocyte antigen (HLA-B27) were better at clearing HIV infection than those with the HLA-A or HLA-C genetic subtypes. HLAs, produced by the major histocompatibility complex (MHC), are by far the most variable region of the human genome, and are an essential part of the immune system. Infected mothers with HIV-protective HLA-B genes were more likely to survive HIV infection and pass on these genes to their children.
It has been proposed that the relatively low level of HIV in Western Europe is aided by a common variation in a co-receptor for the HIV virus particle (CCR5). This variant protects people almost completely against HIV and is found in 13 per cent of Europeans. However it is extremely rare in other populations around the world, including Africans. The origin of the variant in humans dates back thousands of years ago, well before the AIDS epidemic which only dates from the late 1970s. It is therefore likely that this variant may have been selected because it protects against other viral or bacterial infections.
What is inheritance?
Inheritance is the process by which genetic information is passed on from parent to child. This is why members of the same family tend to have similar characteristics.
- We actually have two genomes each
- We get one copy of our genome from each of our parents
- Inheritance describes how genetic material is passed on from parent to child.
How is genetic material inherited?
- Most of our cells contain two sets of 23 chromosomes (they are diploid).
- An exception to this rule are the sex cells (egg and sperm), also known as gametes, which only have one set of chromosomes each (they are haploid).
- However, in sexual reproduction the sperm cell combines with the egg cell to form the first cell of the new organism in a process called fertilisation.
- This cell (the fertilised egg) has two sets of 23 chromosomes (diploid) and the complete set of instructions needed to make more cells, and eventually a whole person.
- Each of the cells in the new person contains genetic material from the two parents.
- This passing down of genetic material is evident if you examine the characteristics of members of the same family, from average height to hair and eye colour to nose and ear shape, as they are usually similar.
- If there is a mutation in the genetic material, this can also be passed on from parent to child
- This is why diseases can run in families.
How is sex determined?
- The sex of an individual is determined by the sex chromosomes called the X chromosome and the Y chromosome.
- Females have two X chromosomes (XX).
- Males have an X chromosome and a Y chromosome (XY).
- Female gametes (eggs) therefore always carry an X chromosome.
- Male gametes (sperm) can carry either an X or a Y.
- When an egg joins with a sperm containing an X chromosome, the result is a girl.
- When an egg joins with a sperm containing a Y chromosome, the result is a boy.
What is a genotype?
- The genotype is a description of the unique genetic makeup of an individual. It can be used to describe an entire genome or just an individual gene and its alleles.
- The genotype of an individual influences their phenotype.
- For example, if we are talking about the genotype for eye colour we may say an individual has one brown eye allele (B) and one blue eye allele (b).
- As a result, the individuals phenotype will be brown eyes.
- This is because the allele for brown eyes is dominant, while the allele for blue eyes is recessive (see image below).
Illustration to show the inheritance of dominant and recessive alleles for eye colour.
Image credit: Genome Research Limited
What is a phenotype?
- The phenotype is a description of the physical characteristics of an organism. For example, if we are talking about eye colour the phenotype of an individual may mean blue, brown or green eyes.
- Most phenotypes are influenced by an individual’s genotype, although environment can also play a role (nature versus nurture).
What is Mendelian inheritance?
- The simplest form of inheritance was uncovered from the work of an Austrian monk called Gregor Mendel in 1865.
- From years of experiments using the common pea plant, Gregor Mendel was able to describe the way in which genetic characteristics are passed down from generation to generation.
- Gregor used peas in his experiments primarily because he could easily control their fertilisation, by transferring pollen from plant to plant with a tiny paintbrush.
- Sometimes he transferred pollen to and from flowers on the same plant (self-fertilisation) or from another plant’s flowers (cross fertilisation).
- In one experiment he cross fertilised smooth, yellow pea plants with wrinkly, green peas:
- Every single pea resulting from this first cross, the first generation (F1), was smooth and yellow.
- However, when two smooth, yellow peas from this first generation were crossed to produce a second generation (F2), the result was 75 percent smooth, yellow peas and 25 percent wrinkly, green peas (3:1).
- This outcome shows that the genes for smooth, yellow peas are dominant while the genes for wrinkly, green peas are recessive.
- The results from this and further experiments led Gregor Mendel to come up with three key principles of inheritance:
- The inheritance of each trait is determined by ‘factors’ (now known as genes) that are passed onto descendants.
- Individuals inherit one ‘factor’ from each parent for each trait.
- A trait may not show up in an individual but can still be passed onto the next generation.
- Genetic traits that follow these principles of inheritance are called Mendelian.
What is genetic variation?
Genetic variation is a term used to describe the variation in the DNA sequence in each of our genomes. Genetic variation is what makes us all unique, whether in terms of hair colour, skin colour or even the shape of our faces.
- Individuals of a species have similar characteristics but they are rarely identical, the difference between them is called variation.
- Genetic variation is a result of subtle differences in our DNA.
- Single nucleotide polymorphisms (SNPs, pronounced ‘snips’) are the most common type of genetic variation amongst people.
- Each single nucleotide polymorphism represents a difference in a single DNA base, A, C, G or T, in a person’s DNA. On average they occur once in every 300 bases and are often found in the DNA between genes.
- Genetic variation results in different forms, or alleles, of genes. For example, if we look at eye colour, people with blue eyes have one allele of the gene for eye colour, whereas people with brown eyes will have a different allele of the gene.
- Eye colour, skin tone and face shape are all determined by our genes so any variation that occurs will be due to the genes inherited from our parents.
- In contrast, although weight is partly influenced by our genetics, it is strongly influenced by our environment. For example, how much we eat and how often we exercise.
- Genetic variation can also explain some differences in disease susceptibility and how people react to drugs.
- Genetic variation is important in evolution. Evolution relies on genetic variation that is passed down from one generation to the next. Favourable characteristics are ‘selected’ for, survive and are passed on. This is known as natural selection.
Record-breaking simulation hints at how climate shaped human migration
Model suggests that a shift in weather patterns in southern Africa might have contributed to the rise of Homo sapiens.
A colossal simulation of the past two million years of Earth’s climate provides evidence that temperature and other planetary conditions influenced early human migration — and possibly contributed to the emergence of the modern-day human species around 300,000 years ago.
The finding is one of many to come out of the largest model so far to investigate how changes in Earth’s movement have influenced climate and human evolution, published in Nature today. “This is another brick in the wall to support the role of climate in shaping human ancestry,” says Peter de Menocal, director of the Woods Hole Oceanographic Institution in Falmouth, Massachusetts.
The idea that climate might have a significant role in human evolution has been around since at least the 1920s, when scientists started debating whether drier conditions had led early human ancestors to begin walking on two feet, to adapt to life on the savannah. But so far, researchers have struggled to provide strong evidence that climate played a part in shaping humanity.
In the latest study, Axel Timmermann, a climate physicist at Pusan National University in South Korea, and his colleagues ran a climate model on a supercomputer for six months to reconstruct how temperature and rainfall might have shaped what resources were available to humans over the past few million years. Specifically, the researchers examined how long-term fluctuations in climate brought about by Earth’s astronomical movement might have created the conditions to spur human evolution.
The push and pull of other planets alters Earth’s climate by changing both the planet’s tilt, and the shape of its orbit. Over 41,000-year cycles, Earth’s tilt oscillates, affecting the intensity of seasons and changing how much rain falls over the tropics. And over 100,000-year cycles, Earth goes from having a more circular orbit — which brings more sunlight and longer summers — to having a more elliptical orbit, which reduces sunlight and can lead to periods of glacial formation.
Timmermann and his colleagues used a simulation that incorporated these astonomical changes, and then combined their results with thousands of fossils and other archaeological evidence to work out where and when six species of humans — including the early Homo erectus and the modern Homo sapiens — could have lived.
Movements and mixing
The study pumped out a dizzying amount of data, and Timmermann says that several interesting patterns emerged. For instance, the researchers’ analysis showed that an early human species, Homo heidelbergensis, started expanding its habitat around 700,000 years ago. Some scientists have thought that this species might have given rise to a slew of others across the globe, including Neanderthals (Homo neanderthalensis) in Eurasia and H. sapiens somewhere in Africa.
The model suggests that the distribution of H. heidelbergensis across the globe was possible because a more elliptical orbit created wetter climate conditions that allowed the species to migrate more widely. The simulation also showed that the most habitable regions, in terms of climate, shifted over time, and the fossil record tracked along with them.
“The global collection of skulls and tools is not randomly distributed in time,” Timmermann says. “It follows a pattern” that overlaps with climate change driven by Earth’s movement. “This is amazing to me — here is a pattern that nobody so far was able to see.”
One part of this pattern might provide fresh insight into where and how our own species emerged. Some genetic studies of modern-day hunter-gather groups in sub-Saharan Africa — who tend to be genetically isolated — suggest that H. sapiens is the outcome of a single evolutionary event in southern Africa. But other studies point to a more complex story, in which humanity began as a hotchpotch of many different groups of ancient Africans that, together, evolved into modern-day humans.
Timmermann and his colleagues say that their climate reconstruction favours the single-evolutionary-path hypothesis. The model suggests that our species evolved when H. heidelbergensis in southern Africa started losing liveable habitat during an unusually warm period. This population could have evolved into H. sapiens by adapting to the hotter, drier conditions.
But this finding is unlikely to end debate. “To make the case that a particular climate event led to a speciation event is really hard”, in part because of gaps in the fossil and genetic record, says Tyler Faith, a palaeobiologist at the University of Utah in Salt Lake City.
The same goes for many of the other patterns reported in the paper. “The people who’ve spent a career studying this will either be in violent agreement or disagreement with the propositions here,” de Menocal says. The model, however, is a “phenomenal accomplishment in and of itself” and “gives you a template to ask these questions”.
Most researchers that spoke to Nature say that more evidence will be needed to prove that astronomical cycles influenced the trajectory of human ancestry. “If solving the mystery of climate change and human evolution could be dealt with in one paper, it would have been done 40 years ago,” Faith says.
Which is why Timmermann and his colleagues are planning to run even larger models, including ones that integrate genetic data.
Why curly hair was an evolutionary advantage
Just why humans have hair on their heads is a long-standing question that few scientists agree on, but the latest research shows that curly hair may have been an evolutionary advantage for our hominin ancestors.
The curls on your head may have originally served as an evolutionary advantage for growing bigger human brains, according to new research that involved studying a bewigged mannequin in a climate-controlled wind tunnel.“The brain is a large and very heat-sensitive organ that also generates a lot of heat,” explains Tina Lasisi, currently a postdoctoral researcher in biological anthropology at Pennsylvania State University. “So we figured, evolutionarily, this could be important—especially in a period of time when we see the brain size of our species growing.”Tightly curled hair better protects the scalp from solar radiation, the new research shows, and it doesn’t lie flat against the skin while wet—a boon in hot conditions that can make humans sweat, like those encountered by our hominin ancestors in Africa millions of years ago.
‘Sweating isn’t free’
A research article by Lasisi and her Penn State colleagues, published this month in the Proceedings of the National Academy of Sciences, describes their measurements of how hair regulates scalp temperature in direct sunlight, using different wigs on a “thermal mannequin.”The mannequin, heated to the average body temperature of 95 degrees Fahrenheit, was placed in a climate-controlled chamber within a wind tunnel that enabled scientists to study the amount of heat transferred between its skin and the surrounding environment.Three wigs were made from black human hair sourced from China—one straight, one moderately curly, and one tightly curled—so that the researchers could observe how different hair textures affected heat gain and loss on the scalp. They also calculated heat loss at different windspeeds, after wetting the wigs to simulate sweating.The researchers then made a model of heat loss under different conditions and studied it under the typical conditions in equatorial Africa where early hominins are thought to have evolved.
They learned that all types of hair gave some protection from the sun, but tightly curled hair gave the best protection and minimized the need to sweat—a significant finding, says Lasisi.“Scalp hair is… a possible passive mechanism that saves us from the physiological cost of sweating,” she says. “Sweating isn’t free—you’re losing water and electrolytes. And for our hominin ancestors that could have been important.”
The mystery of human hair
Just why humans have hair on their heads is a long-standing question that few scientists agree on.Many link it to our evolution from four-legged creatures to those that walk upright, reasoning that head hair helped regulate the body’s temperature by acting as a barrier to the equatorial sun.Niccolo Caldararo, an anthropologist at San Francisco State University who wasn’t involved in the latest study, favors evolutionary anthropologist Dean Falk’s “radiator theory” : that hair protects large hominin brains in hot sunlight and insulates them when it’s cold.
But Caldararo notes it’s a complex subject with many variables: for example, white hair that reflects light might be better protection from the sun than black hair that absorbs its heat, he says.The research by Lasisi and her colleagues is “provocative,” says Kurt Stenn, a dermatologist not involved with the study and the author of Hair: A Human History. He suggests that the researchers should have also considered the shape and density of human head hair.
For example, the Asian hair used in the study tends to be round in cross-section and therefore absorbs more heat than some types of African hair, where each hair is shaped like a long ribbon that curls more easily, he says.Evolutionary biologist Elizabeth Tapanes at the University of California San Diego, who also wasn’t involved in the study, says the research is “a great leap forward about thinking why we have so much hair on our heads.”She adds that studying the hair of other primates alongside human hair could help scientist better understand how it keeps the head cool; her own studies of lemurs called sifakas have found similar results.Sifakas are vertical climbers and leapers, so they are usually upright with their heads facing the sun, Tapanes says; and the researchers found they had more scalp hair and less body hair in hot and humid environments.
An evolutionary advantage?
It’s even possible that curly hair might be one of the reasons why Homo sapiens supplanted the Neanderthal and Denisovan species of hominins, which died out about 40,000 years ago.Lasisi points out that if the genetic mutations for curly hair occurred before Homo sapiens left Africa, but after our hominin ancestors did, it might have given early modern humans an evolutionary advantage.But she doesn’t think that’s likely; and the study proposes instead that genes for curly hair arose much earlier in human evolution, perhaps around two million years ago when Homo erectus was the dominant hominin. And as hominin brains grew bigger, it suggests, the genes for curly hair that protected the scalp from the sun may have given those who had them an advantage.As for straight hair: Lasisi says any genetic predisposition for curly hair among early hominins was probably variable. “We don’t expect that it would have been homogenous,” she says. At a later point in our evolution, curly hair may have lost its evolutionary advantage, and straight hair may have been favored by different types of genetic selection.
“Maybe once we had those larger brains, we also had all these cultural adaptations to avoid overheating, like better sources of water,” she says. “And at that point, maybe there wasn’t such a selective pressure for curly hair.”Lasisi says the next stages of the research will be to look for genetic evidence that may support the theory.“First, we’ll have to know more about modern humans, such as which genes are associated the hair morphology,” she says. “And the second step will be to collaborate with people who do ancient DNA work, to see if those are seen in archaic humans.”
Natural selection and evolution are the order of things. They are the forces that have driven our natural history, and are responsible for the diversity of life on this planet. This is how we came about. However, Homo Sapiens as the dominant species have been artificially changing these forces. We have been using technology and our ability to reason to gain an unfair advantage and to change our environment. Many people have reasoned that our increased Carbon Dioxide footprint has accelerated global warming to such an extent that many species cannot adapt quick enough to survive. We have also hunted countless species to extinction. The definition of cancer is a disease caused by an uncontrolled division of abnormal cells in a part of the body. The human species, through the instrument of culture, has become the dominant force of planetary ecological change. Our adaptations have become maladaptive. Moreover, the human species as a whole now displays all four major characteristics of a malignant process: rapid, uncontrolled growth; invasion and destruction of adjacent normal tissues (ecosystems); metastasis (distant colonization); and dedifferentiation (loss of distinctiveness in individual components). We have become a malignant ecopathologic process.
We have violated the laws of natural selection by maintaining non viable life through technology, in a misconception that we are improving life. I have been a Registered nurse for 19 years and an ICU nurse for 9 of those years. I have see life prolonged in a hopeless attempt to alter our evolutionary and aging process. We are in some cases causing needless suffering in an attempt to prolong the lives of patients with terminal illnesses. In some cases this is being done against the patients expressed wishes. We are also through the miracles of modern medicine and nutrition we are extending the lifespan of the human race. In many cases those additional years are not ones of joy and abundance, but of disease, weakness and senility. In the animal kingdom those individuals would be attacked and killed by predators, thereby conserving resources. In the animal kingdom on the strongest individuals in the species survive to reproduce. In the human race weak and feeble individuals, and others with genetics disorders (such as Down’s Syndrome, Sickle Cell Anemia) continue to breed, thereby continuing in perpetuity these disorders. If natural selection was truly allowed to work in the human race these disorders would be virtually non existent. Don’t get me wrong I am not saying we should kill people off or castrate these individuals. I am strictly speaking in a evolutionary manner.
One of the more optimistic theories in ecology has been the Gaia hypothesis, which holds that the entire planet is a self-interacting system that balances itself and regulates the status of life everywhere. Gaia keeps life in a healthy state, just as the mechanism of homeostasis in the human body works to keep every cell healthy and in balance. But bodies die from cancer, and one wonders if the human race is a cancer that the planet cannot correct for. If all of life constitutes a single “superorganism,” how much adaptability is left in that organism? Like a malignancy, the basic problem with Homo sapiens is that we want to take over everything. We want to expand without regard for other life forms. Eventually, like cancer, our destruction may be caused by our very success. In its insatiable urge to dominate, a cancer cell drives away all competition, but in so doing it wrecks the body’s ecology and therefore is doomed. Gaia, or the total ecosystem if you prefer, has accommodated human life as one species among many, but it is hard to see any planetary mechanism that can check the spread of humans in so many destructive areas. Of course, the fact that we may pollute ourselves out of existence can be accommodated ultimately. should the human race reach its end game, other life forms will persist and carry on without us. Has the planet reached its limit as an ecosystem that can include us? If not, how close are we? The human body is so masterful at self-correction, I wonder if there is a similar self-correcting mechanism in the human mind that can be called upon, or that will assert itself in the coming generations.
Recent studies carried out involving the Hadza Tribe and of Lions in Africa, have shown that scavenging as previously proposed is not a sustainable means of survival for primitive tribes. Scientists examined carcasses and bones left over from lion kills and of prehistoric bones found with ancient villages. When the carcasses were examined after the lions finished eating their fill, there was simply not enough meat left to support scavengers. Also the bit marks do not match up. Typical puncture marks from predators were not found on the ancient bones, instead weapon marks were found showing that our ancestors were hunters not scavengers. It is estimated that high protein diets helped increase brain main at a much more rapid level than did strictly herbivorous diets.
Scientist have also postulated that after examining our family tree, that those branches that were able to act as specialists and generalists. Many of the dead end species were not able to adapt to environmental changes. For example the Neanderthals were big game hunters, when the weather changed and the numbers of bug game died out they were not able to adapt to these changes. Some genes however, were preserved due to species intermingling. The Neanderthals were blocky and heavily built, they were simply not built for speed. So when animal species became smaller and faster, they were not able to adapt and eventually died off. The Cro-Magnon Man, were not as specialized and were able to adapt better to the changing landscape. (Updated 8/14/2021)
Enter the covid-19 virus, Is this our tool of natural selection? It is a simple strand of genetic material that is kicking our asses. It seems to be geared towards the elderly, sick, obese and feeble individuals. It could very well be nature’s way to relieve the pressure that the human race is putting on the planet. In fact, acting to bring about a natural selection cleansing of our species. So my question is should we just allow it to run its course? By stopping the lock downs and opening up our world economies. Yes we can still fight it and work on vaccines, but should we allow herd immunity to take its course? You may ask the question, has modern medicine and our civilization helped to keep alive weaker gene pools? Please realize that I am not in any way proposing that we let people die. I am simply posing topics a for discussion and debate. What do you think?
If alien life exists in our solar system, it may look like this
Pictures of deep-sea vents hidden below ice offer some of our first looks at creatures thriving in conditions akin to those on watery moons.
ICEBREAKER R.V. KRONPRINS HAAKON, OFF GREENLANDOutside, the sinking sun is coloring the autumnal sky a brilliant lavender, a rich hue that lingers over a vast blanket of ice. Here, off the northern coast of Greenland, the Arctic Ocean is masquerading as land, a snowy patchwork of smooth ice floes and abrupt, jagged piles of crystalline debris. Only the subtle shifting of our ship, the Norwegian icebreaker R.V. Kronprins Haakon, betrays the landlocked illusion.
It took longer than expected to get to this icy wonderland from the small coal-mining town of Longyearbyen, the most populated port in Norway’s Svalbard archipelago. Now that we’re here, Chris German isn’t paying much attention to the dramatic seascape. Instead, he’s staring intently at a live feed of the seafloor, and he’s trying on hats. Every 10 minutes or so, he plops a different hat on his head, rotating through haberdashery that includes a faux sealskin ushanka, a woven orange fez, and a beanie from the Woods Hole Oceanographic Institution, where he works.
The costume changes help German pass the time while we wait for the first glimpse of our quarry: a broken patch of seafloor that’s pumping smoky, superheated fluids into the darkness, perhaps helping to power one of the most alien ecosystems on Earth. This elusive zone is called the Aurora hydrothermal vent field. It’s the most northerly vent field yet known, and it’s among the deepest in the world, sitting nearly 2.5 miles below a permanent covering of sea ice.
Exploring the deep sea, like venturing into deep space, is a high-risk endeavor. The abyssal seafloor is an unforgiving place for even the hardiest robots, and this mission has seen its share of mishaps, including a few heart-stopping days when it seemed like the team had lost its main underwater rover to the freezing polar ocean.
But on this violet evening, after hours of drifting over a muddy seafloor, a high-resolution camera towed beneath the ship at last passed directly over a gaping maw in Earth’s crust. Beamed onto screens throughout the ship, the footage revealed an angry black plume erupting from a crater measuring nearly five feet across—an astonishing span for this flavor of undersea smoker.
“That is a big f***ing plume,” German said, his rotating headgear paused on the ear-flapped ushanka. “This is a lot more than we knew was here.”
Later that night, the same camera would fly over the site twice more; and multiple passes over the next week would reveal wildly rugged terrain populating the southern slope of the Aurora seamount. The images revealed that the vent field is covered with extinct chimneys, heaps of extruded minerals, and not just one, but at least three black smokers.
The results offer our best look yet at such an exotic, ice-shrouded ecosystem. Better understanding this remote biosphere could help scientists figure out how creatures move through Earth’s deep oceans, and whether Arctic waters form a pathway for animals moving between the Atlantic and Pacific basins.
“The idea is to really understand this area when it’s still pristine,” says deep-sea ecologist Eva Ramirez-Llodra, the project’s lead scientist from the Norwegian Institution for Water Research. “If climate change gets rid of the ice, this will become a more used route to go to the Pacific, and it could become an open area for potential mining, for fisheries … it’s good to know what’s there.”
What’s more, the Aurora vents could hold the keys to detecting life-forms in the deep oceans on alien worlds. For now, Aurora is one of the closest Earth-analogs to the seafloor vents that are thought to be erupting on faraway ocean worlds, including the ice-encrusted moons Europa and Enceladus, which are considered among the best places to look for existing extraterrestrials. (Find out more with our interactive atlas of moons.)
“Alien oceans beyond Earth are so compelling in the search for life elsewhere,” says National Geographic Explorer Kevin Hand, an astrobiologist at NASA’s Jet Propulsion Laboratory who took part in the Aurora expedition. “Wherever we’ve looked on planet Earth and found liquid water, we’ve found life.”
Plethora of vents
In general, oceanic hydrothermal vents arise when seawater seeps through cracks in Earth’s crust and mingles with hot rocks beneath the surface; those buried molten rocks heat the saltwater and fuel chemical reactions that erupt in a roiling mass through vents in Earth’s crust. The continual extrusion of mineral-rich, superheated seawater provides the heat and energy needed for some organisms to thrive in these cold, dark depths, including a menagerie of vent-specific gigantic tube worms, foot-long clams, blind shrimp, and extreme microbes.
For a long time, canonical wisdom had suggested that hydrothermal vent activity could only exist at the fastest spreading mid-ocean ridges—places like the East Pacific Rise, where Earth’s tectonic plates are hustling away from one another at speeds of around seven inches a year. At these bursting planetary seams, the brisk spreading of Earth’s crust means that fresh magma is always available to fuel the vents.
Over the years, though, German and his colleagues have found vents populating a variety of ridges, including some that languidly go their separate ways. Our most recent target, the Gakkel Ridge, is a volcanic rift bisecting the Arctic Ocean that is spreading at the stultifying rate of less than half an inch a year.
“Nowhere is precluded from having hydrothermal activity,” German says. “We can dispense with that myth now.”
Scientists first went prospecting for hydrothermal plumes along the Gakkel Ridge in 2001. During that cruise, a layer of murky water detected near the seafloor hinted at vent activity, and a rock-dredge pulled up the remains of an extinct chimney. Both observations could be explained by black smokers, the sort of vents that launch towers of dark, hot plumes into the water.
During a second cruise in 2014, German and his colleagues returned to Aurora aboard the icebreaker Polarstern. They searched for vents by looking for hydrothermal signatures in the water column and, toward the end of the cruise, they dropped a high-resolution camera into the deep. Just two hours before it was time to head home, the team caught their first glimpse of a small chimney, a fleeting photobomb by a smoking vent that slid into the margins of several frames.
But the vent signatures written into the freezing sea suggested that something much more massive must lie below. Buoyed by that discovery, this year’s expedition, known by the acronym HACON, aimed to put the Aurora vent field into context. How extensive is the entire system? What kind of chemistry is involved? Can the vent support a deep-sea ecosystem, and if so, what kinds of organisms live there?
And, for the astrobiologists on board, what insights might the site bring in efforts to detect life on ice-covered ocean worlds across the solar system?
Answering these questions presented challenges even before the icebreaker left port. The high-resolution camera that proved so vital to the mission, called the Ocean Floor Observation and Bathymetry System, or OFOBS, was initially mis-bundled with gear destined for a different polar expedition. Worse, a deep-diving, remotely operated submersible from Woods Hole called Nereid Under Ice, or NUI, was very nearly lost to the deep.
NUI is a state-of-the-art, $2.5-million submersible roughly the size of a minivan. It can spend half a day underwater before being recharged, can swim more than 25 miles from the ship, and can dive three miles down without imploding, allowing it to work under thick ice cover.
The bright orange submersible has an on-board brain that lets it function human-free, yet it can also be remotely piloted, meaning that scientists watching a live feed from its cameras can tell it to pluck specific animals from the deep-sea floor, dunk collecting tubes into particular sediments, and dip specially designed probes straight into the effervescent, sulfuric fluid erupting from a hydrothermal vent. Geochemist Eoghan Reeves of the University of Bergen, who once (accidentally) took a swig of the seafloor libation, and says the bubbly mixture resembles bad champagne: “It smells just terrible, and it tastes exactly like it smells.”
But two days after arriving at the Aurora seamount, NUI dove and did not come back up. As the sub neared its target depth, its onboard systems blinked off one by one. Engineers tried to coax it to float back up on its own, triggering a fail-safe mechanism that should have released its dive weights and restored buoyancy. Instead of rising, NUI stopped moving, its depth reading becoming a foreboding line that marched across a screen in the ship’s control room.
“The likelihood that it’s resting on the bottom is pretty high—in which case, game over,” Andy Bowen, director of WHOI’s National Deep Submergence Facility, finally said. Without NUI, even catching a glimpse of the vent meant relying only on OFOBS, the high-resolution camera. But that camera isn’t steerable and could merely be towed along behind the ship, which meant that successfully spotting the undersea plume depended on cooperatively drifting ice or floes thin enough to break.
“We knew coming out there would be difficult, that we would face challenges, but this is beyond any of our expectations,” said Benedicte Ferre, a physical oceanographer at the University of Tromsø.
Mordor of the deep
Fortunately, NUI resurfaced after three days; the fail-safe had simply taken a little longer to work than anticipated. Even better, while NUI was being fixed up, the icy patchwork covering Aurora allowed the ship’s captain to fly the OFOBS camera directly over the Aurora vent site.
That evening, scientists were clustered around TV screens throughout the ship, anxiously watching the seafloor drift by under the inky twilight. Soon, a layer of nearly black gravel crept into view, carpeting the sticky beige mud that had slid by for hours. Brilliant orange and yellow patches appeared, and the camera began climbing, moving up a stunningly steep, craggy wall.
The 50-foot-tall formation came out of nowhere—pinnacles of volcanic material vomited from beneath the seafloor. The pumice-like sediments grew darker and darker, and then, for a moment, a violently churning cloud tickled the corner of the image, followed by the curving jaw of a giant, toothed crater. As the ship drifted, the cloud expanded into a massive black plume that engulfed the camera and continued billowing upward for nearly half a mile. This smoker was clearly a behemoth that dwarfed the average chimney. Later tows would reveal even more black smokers on the seafloor.
“Satanic, like the satanic mills of the Industrial Revolution. Mordor,” German said of the giant vent. “We knew there had to be more than what we saw in 2014.”
Based on the extensive heaps of sulfides and extinct chimneys, the Aurora vents have almost certainly been active for millennia, perhaps seeding the Arctic seafloor with heat and minerals since before humans first arrived in the Americas.
But exactly how long the site has been erupting is still an open question, as are many of the other mysteries the team set out to solve. Without many samples from the site’s life-forms, for instance, the team doesn’t have the genetic material needed to easily answer several of their pressing questions about how creatures move between ocean basins.
More puzzling, at least in some ways, is that the Aurora ecosystem appears to be unusually sparse, at least in the images collected from this cruise. Here, there are no obvious tubeworm meadows, sharp beds of mussels, or colorful carpets of anemones. Even microbial mats, although visible in some areas, are conspicuously lean. This vent, it seems, is the realm of small snails and scavenging, shrimp-like crustaceans called amphipods.
“It’s nothing compared to vents in other oceans, where you have huge amounts of animals,” says Ramirez-Llodra, who adds that “we just have a few images. And they are great images, but we haven’t really surveyed the area in detail.”
Ana Hilário, an ecologist from Portugal’s Universidade de Aveiro, was particularly stunned by the absence of Sclerolinum, a type of polychaete worm that’s abundant elsewhere in the deep sea. She and Hans Tore Rapp, a taxonomist from the University of Bergen, suspect that the Arctic seafloor might be sparsely populated primarily because the north polar ocean is still geologically young—roughly 60 million years old—and deep-sea fauna may not have had enough time to find their way into these waters and adapt to the extreme conditions.
The only organisms that really appear to thrive in the area are two types of glass sponges, creatures named for their filigreed, glassy skeletons. Sometimes measuring more than three feet across, and with lifespans predicted to span centuries, these glass sponges are occasionally said to be barely alive. Perhaps less than five percent of their biomass is organic, and the rest is silica, the same stuff that makes sand and glass. Fortunately, NUI dove to the seafloor after being fixed up and collected some glass sponges from a spot near the vent.
Rapp suspects that these sponges can thrive in a potentially nutrient-starved, carbon-choked ecosystem precisely because they don’t require much particulate organic carbon. Instead, they’ve adapted to survive on low concentrations of dissolved organic matter and make their skeletons out of more readily accessible building blocks.
“Silica in the deep is always easily available,” Rapp says. “There’s almost no cost to build skeleton.”
The observations raise some tantalizing possibilities for what might be lurking in the seas beyond Earth, where sunlight is scarce and the only reliable form of energy might be chemically generated by the heaving innards of an ice-crusted moon.
Kevin Hand says that a lot of the work he’s doing at NASA involves figuring out what kinds of biosignatures to look for in the icy sheaths cocooning alien seas. That’s one of the reasons he’s studying Aurora’s ice, to figure out if it holds signs of the life-supporting vents that scientists can learn to recognize—on Earth and, perhaps, on other worlds.
“Using the ice as a window to the ocean below,” he says, “this is relevant to how we actually learn about these oceans that are beyond Earth.”
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