Thursday, 19 March 2015

Creationism Fails Again - Human Evolution in 2014

Like 2013, 2014 has been another very bad year for creationism as more and more of those 'missing' intermediate fossils are found and the human evolutionary story becomes more and more complete.

Perhaps I should say it's been a good year for those who might be tempted to believe the disinformation put out by creationist pseudoscientists but who still remain objective and open to evidence and reason.

Diehard fundamentalist creationists of course will remain stoically and proudly resistant to evidence, no matter how strong it may be, simply waving it away as wrong or lies, so we are never going to see a committed creationist, least of all one who earns a living by misinforming others, announcing that this or that piece of evidence has convinced them that they have been wrong all along. In many cases, that degree of honesty would be more than their job's worth and would earn them the immediate approbrium of their colleagues.

This little list was produced by a quick search of the science magazine sites. I don't claim it to be exhaustive or even particularly representative, only a random sample of the sort of science shedding light on the human evolutionary story and the way it is growing and being clarified and missing detail being filled in, not just from palaeoanthropology either; DNA sequencing is adding a huge amount of detail as is the related study of comparative protein analysis.

The remarkable thing is not so much how well the evidence from disparate scientific disciplines is messing neatly together but that there are still people who won't accept it but cling stubbornly to a superstition for which not one shred of credible scientific evidence exists.
  • March 2014 Is light skin in Europeans and Asians a very recently evolved attribute? New Diet, Sexual Attraction May Have Spurred Europeans' Lighter Skin | Science/AAAS | News. A new study suggests a combination of change in diet as we changed from hunter-gatherer to farmers, and sex selection may have been the main drivers for the evolution of lighter skin.

    The evidence is that Europeans may have had dark skin up to about 8000 years ago. As we changed our diet we may have reduced our dietary intake of vitamin D - essential for normal bone development. In the cloudier northern latitudes, lighter skin allows more vitamin D to be made by the action of UV light on skin but increase the risk of skin cancers. The balance was shifted in favour of light skin and this change may have been accelerated by sex selection.
  • Epigenetic mechanisms by National Institutes of Health.
    Licensed under Public Domain via Wikimedia Commons.
  • April 2014 Where do new genes come from? Seeing double: New study explains evolution of duplicate genes - ScienceDaily. We know that a typical genome has lots of duplication - apparently about 50% of the human genome consists of duplicated DNA, some of which has since mutated and been exapted for other functions. The question is why did this redundant DNA hang around?

    Now a team sponsored by the National Science Foundation, based at the Parker H. Petit Institute for Bioengineering and Bioscience at the Georgia Institute of Technology has shown that this is related to the fairly recent discovery of epigenetics.

    Epigenetics is the study of the way genes are switched off in different tissues. For example, whilst all cells have the same genes, obviously a muscle cell, for example, doesn't use a lot of the genes used by a liver or a brain cell, and they don't use a lot of the genes needed by skin cells or bone marrow. So, the 'redundant' genes in each of these tissues are switched off by a methyl group being attached to a key position which prevents them being expressed. This is termed 'methylation' and the same process of methylation is used to switch off accidentally duplicated genes too. Since they don't express, there is little for natural selection to select against, so they simply hang around and get duplicated along with the rest of the genome.

    However, because they don't express, there is nothing to prevent them mutating randomly without doing any harm, and occasionally, they may produce a new protein with a new function that gives an advantage. There are many examples at the cell level of proteins performing very different functions but which are clearly related and a lot of these are to be found in the brain. The team showed that in all the ten human tissues studied, the recently duplicated genes tended to be much more heavily methylated than their originals.

    This of course gives the lie to creationist pseudoscience claims that mutations are always harmful, and that somehow the Second Law of Thermodynamics prevents new information from arising by mutation. Incidentally, has anyone ever had an intelligible response from a creationist who has been asked to explain the science behind why they assert this observable phenomenon to be impossible? Me neither.
  • May 2014 Humans are weak and puny, big-headed apes. Humans Gave Up Our Strength to Support Our Big Heads | Smart News | Smithsonian

    Of all the great apes, humans are by far the weakest physically. An adult Chimpanzees is about three times stronger than an adult human yet this difference must have developed in the 6 million years since we diverged. Given that gorillas and orangutans are also much stronger than we are and, weight for weight, even gibbons and siamangs are much stronger than us, it seems highly likely that our evolution has resulted in a loss of muscle - which seems counter intuitive. Why would losing physical strength give an adaptive advantage on the plains of East Africa and the Ethiopian Highlands?

    A team of researchers believe they have found the answer - it was a trade off between a bigger brain and brawn, besides, given that we had given up an arboreal existence so didn't need the upper-body strength to swing through trees, and had evolved a shoulder making us good at throwing and a hand good at making things to throw, we needed brains rather than brawn. Brains take a lot of energy and nutrient to grow so by diverting this to growing a bigger head at the expense of growing bigger muscles, we became more successful as a species - or rather our early ancestors did because this process started way back in our evolution.
  • July 2014 Was there ever a distinct Homo heidelbergensis? RIP for a key Homo species? H. heidelbergensis has always been controversial and some think the evidence is too weak to sustain it as a distinct species inhabiting Europe, Africa and Asia and being directly ancestral to H. neanderthalensis and Denisovans in Euro-Asia, and H. sapiens in Africa. Some put the African specimens into a separate species - H. rhodesiensis. Evidence of the remains found in Sima de los Huesos in Spain which were thought to be H. heidelbergensis is being shown with DNA analysis to be closer to H. neanderthalensis or even Denisovans, and could be those of H. antecessor.

    In addition, the range of variance found in H. erectus from a single site at Dmanisi in Georgia, south of the Caucasus Mountains, suggests palaeoanthropologists may have been too quick to assign different species to specimens from Africa that all fall within the H. erectus range. As always, the problem lies in exactly where to draw a line between an archaic species and the one it gradually evolved into, complicated by different rates of evolutionary change over the whole range, and even a degree of interbreeding with the incompletely differentiated species acting as a ring species.

    This part of the human evolutionary story is continuing with healthy debate and doubt driving a search for definitive evidence one way or another.
  • July 2014 Evidence of interbreeding between related species of Homo. Tibetans inherited high-altitude gene from ancient human | Science/AAAS | News. The Tibetan people living high in the Himalayas have adapted to high-altitude life with low oxygen pressure which would cause severe long-term problems for other people. It was believed that this adaptive mutation arose in Han Chinese who are closely related to Tibetans in particular in a gene known as EPAS1. However, a new study found that only 2 of 40 Han Chinese had the DNA sequence found in Tibetans and a search of a database of 1000 human genomes failed to find anyone else with the same sequence.

    But, a close match was found instead in the archaic Denisovan DNA from Siberia. This suggests that the Han Chinese may be descended from people who interbred with Denisovans and still retain up to 2% of their DNA but the EPAS1 was only retained in the Tibetans as the two groups split because natural selection at high altitude gave the Tibetans a survival advantage. The Han may have lost it over time, or even re-acquired it from the Tibetans. Either way, this is strong evidence of interbreeding between modern and archaic hominids with the genus acting, at least in Asia, as a ring species with incomplete differentiation or evolution in progress.
  • Image credit: John Lund/Blend Images/Corbis
  • September 2014 Why do we each have a unique face? We Evolved Unique Human Faces So We Could Tell One Another Apart | Smart News | Smithsonian Something we take for granted is facial differences between individuals. It's how we recognise people. But this was not always so. Although there are differences between individual chimpanzees and bonobos, our closest relatives, they are nothing like as varied as between individual human beings, even closely related ones.

    A team of researchers from the University of California found that not only is there more variability in the genes that control face shape than for any other physical feature such as height, but that this variability is even seen in Neanderthals, indicating that it was probbaly so for out common ancestors. Facial recognition is essential for a cooperative society to works effectively so there would have been a distinct adaptive advantage for a cooperative species in which variability is maintained.

    However, the researchers also point out that sex selection could, and probably did, play a part in facial diversity, so we have an evolutionary balance between distinct facial types but considerable variability within those broad types. The fact that earlier hominids had this variability in facial features suggests they too formed cooperative groups. Did the human ability to recognise patterns, which may have given rise to so much in our cultures, including religion, evolve to recognise one another's faces?
  • October 2014 Have we 'domesticated' ourselves? How we tamed ourselves—and became modern | Science/AAAS | News. A symposium at the Salk Institute for Biological Studies heard compelling evidence that, by selecting for reduced aggression in males, which gave greater social stability and enables us to work better in cooperative groups, man underwent a similar process to that seen in other domestic animals, especially dogs, where loss of aggression has resulted in a flatter face, a general feminisation of facial features and a tendancy towards neotony or retaining child-like features into adulthood.

    A similar process was observed in the silver fox when a Russian team subjected them to a process of taming by selecting the least aggressive and least likely to run away from food as humans approached. Changes observed were similar to the differences between domestic dogs and wolves. Bonobos were also cited as an example of a self-domesticated ape with similar results compared to the 'wild' chimpanzees.

    The suggestion is that the genes which control testosterone levels are linked to those controlling facial and cranial development, so reduced testosterone in males and reduced stress levels, not only allow cooperative cultures to develop but also result in the skull changes observed over the last few hundred thousand years of human evolution from Homo heidelbergensis, H. rhodesiensis or even H. erectus to H. sapiens.
  • November 2014 Were Neanderthals a distinct species to modern humans? Were Neanderthals a sub-species of modern humans? New research says no - ScienceDaily. Frankly, my dear, I don't give a damn. I couldn't really care less whether taxonomists finally agree that Neanderthals were a subspecies, a regional variety or a distinct species, or agree to differ.

    It it beyond doubt that they evolved from the same immediate common ancestor as Homo sapiens did, and probably did so in Euro-Asia while modern humans were evolving in East Africa. How far they had diverged and whether they had diverged sufficiently to be regarded as a distinct species or whether they evolved from H. erectus, H. antecessor or H. heidelbergensis, if indeed they were separate species, is of academic interest only. We know they interbred occasionally with our ancestors because non-Africans have some of their genes, so we know they were close to us. We also know that modern humans, Neanderthals and Denisovans behaved like an incompletely differentiated ring species and this all fits perfectly well into an evolutionary model of a widespread species.

    But this is enormously embarrassing for creationists of course because the fact that the term 'species' is difficult to define and that we can't definitely say that H. neanderthalensis was a species or that H. sapiens neanderthalensis was a subspecies, gives the lie to their claims that there is a categorical difference between evolution that gives rise to varieties and subspecies and that leading to different species. It also gives the lie to creationist claims that H. sapiens is a special creation and that there were ever a single ancestral couple from which we are all descended, and which committed some original sin that we all need forgiveness for. That's their problem, not mine. That's what comes of having a superstition which is at odds with known facts.
  • Rhodopsin-transducin uploaded by Dpryan.
    Licensed under Public Domain via Wikimedia Commons.
  • December 2014 Evolution of colour vision in humans has been traced back 90 million years. A clear, molecular view of how human color vision evolved - ScienceDaily. Scientists have worked out every step in the evolution of human vision at the molecular level. Not surprisingly, we have exactly the same colour vision as our closest relatives because it evolved in our remote common ancestor.

    Unlike the parody version that creationist frauds such as Michael J. Behe pretends is how evolution works, when he writes books based on the false claim that lots of highly unlikely mutations have to occur simultaneously in a single individual, colour vision evolved the way proper evolutionary biologists understand it to works - gradually, by an accumulation of small changes over a very long time and in the entire gene-pool. And, of course, it confirms that we share a common ancestor from some 90 million years ago.

So, another year of scientific investigation and not one single paper finding anything remotely like supporting evidence for special creation on an Earth that is only a few years old and every one completely consistent with the scientific view of evolution over a very long time on a very old Earth. Another year in which it has become more and more difficult to maintain a belief in Biblical creationism without ignoring more and more evidence or having to think up more and more idiotic ways to dismiss it. Has this impacted on the disinformation being output by the creation industry, or the determination of the extreme political right in America to subvert the US Constitution and get biblical creationism inserted in the public school science curriculum? Of course not! When did facts and truth have anything to do with it?

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1 comment :

  1. Great article. Very inclusive, accurate and best written articles I've read for some time. Thank you

    ReplyDelete

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