Posts Tagged ‘Human Evolution’

New find from Dmanisi ‘rewrites’ human evolution….again.

21/10/2013

There’s been much speculation in the press about the science paper that described the discovery of a complete skull and mandible from Dmanisi:

A Complete Skull from Dmanisi, Georgia, and the Evolutionary Biology of Early Homo David Lordkipanidze et al. Science 342, 326 (2013); DOI: 10.1126/science.1238484

Once again we’re treated to headlines and badly informed speculation about how the ‘textbooks are going to have to be rewritten’. In reality this is not going to impact that much. Nothing like the impact of say the discovery of H. floresiensis. We have always known that there are problems applying the bio species concept to fossils – especially when dealing with hominins as the record is so fragmentary. Coupled with the fact that the taxonomic status of H. habilis and H. rudolfensis has been very questionable for the last 15 years and the story as the press have presented it loses part of its sensational gleam. The find is amazing and does represent a massive contribution to our knowledge of Homo ergaster/erectus – effectively extending our understanding of intra-specific variation. But while this extends what gets given what label the impact is really going to be a semantic one rather than anything else….

 

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The Evolution will be Televised

21/12/2012

I disagree with Johnjoe McFadden’s criticisms of Steve Jones, but genetics are not the only factor in our species’ survival

Originally published by the Guardian 24th January 2007

http://www.guardian.co.uk/profile/simonunderdown

The geneticist Steve Jones has announced that human evolution has stopped. This is based on a genetic view of the evolutionary process and while it is almost certainly true from a gene-centric perspective, it is really only addressing a small part of what it is to be human. While Jones is absolutely right when it comes to the slowing down of the effects of natural selection on the human gene pool, human evolution is not a purely genetic affair and the path of our development as a species cannot possibly be understood without an examination of the role played by cultural adaptations.

The course of human evolution has displayed a complex relationship between biological adaptations (such as bipedalism or brain size) and cultural adaptations (such as tool use) since the development of the first stone tools, around 2.6 million years ago, in East Africa. The appearance of stone tools in the archaeological record was a major cultural adaptation that provided our ancestors with the ability to manipulate their environment – a process that lead to ever more complex behavioural innovations and one that has continued ever since.

Our earliest hominin ancestors were very different in appearance to us – if still extant, they would look to us very “ape-like”. This was the case for approximately five million years until the appearance, two million years ago, of Homo ergaster – the first human and the first to rely heavily on cultural adaptations rather than biological ones. The process of human evolution from two million years ago onwards was one of relatively small-scale biological changes in tandem with massive and far-reaching cultural development. It was the development of cultural adaptations that provided the basis for our evolutionary success and produced the current genetic pattern that Jones describes. The use of cultural adaptations, such as fire and clothing, removed the need for biological adaptation and meant that the basic body plan of the genus Homo has remained relatively unchanged. Although there are of course differences between species such as Homo ergaster, the Neanderthals and Homo sapiens, the factor that unites us all was the role that cultural innovation played in allowing a wide range of habitats to be exploited without the need for biological adaptation. Massive increases in intelligence, a biological process, provided the raw material for a huge range of cultural adaptation and environmental manipulation.

Johnjoe McFadden argues that Jones’s view is incorrect and that the role of genetic engineering means that we will be soon be entering a period of evolutionary dynamism – a result of being able to tweak our genome to, for instance, remove cancer and other genetic diseases – an interesting idea but it overlooks the fact that many of these diseases take hold later in life, after reproduction, and as such could be argued to be relatively selectively neutral. Genes are not the only factor; the environment plays a huge role in our makeup. Simply put, genetic predisposition to heart disease is not the same as heart disease!

Ultimately, genetics is only part of the story of human evolution. While the process of genetic evolution is clearly slowing down and we are no longer subject to the widespread effects of natural selection, cultural evolution continues to play a crucial role in the development of the human species as it has done for nearly 2.6 million years. The pace of cultural adaptation is still moving rapidly and producing a greater range of variation than at any other time in our evolutionary history. We may be heading for a homogenous genetic future but the human evolutionary story tells us that our culture will continue to evolve and flourish as long as humans are around.

An Evolving Tale

21/12/2012

We should not underestimate the importance of climate change – humans are part of the environment, not masters of it.

Originally published by the Guardian 3rd April 2007

http://www.guardian.co.uk/profile/simonunderdown

There really seems to be very little doubt that human activity is responsible for climate change: atmospheric concentration of CO2 (a major cause of global warming) is now significantly higher than at any time over the last 600,000 years. The start of this massive increase coincides very closely with the genesis of the industrial revolution.

We should be worried about the effects of climate change, not just because of the short-term problems it will undoubtedly lead to, but also because of the long-term issues we can only guess at. The media is full of speculation about the effect of relatively short-term climate change, such as rising sea levels and desertification.

Yet it is worth examining just how powerful a hold climate really has on our species from an evolutionary perspective. It would not be going too far to say that climate change has been one of the major factors in human evolution (the other is, of course, technology). A drop in global temperature during the Miocene epoch approximately 8-10 million years ago, resulted in the fragmentation of the large African forests, which in turn led to the development of savannahs (wide open grassland). It was this incidence of climate change that seems to have kick-started human evolution.

Around 7 million years ago our early ancestors ventured out of the forests and onto the savannah, slowly adapting to this new environment (while the ancestors of chimpanzees stayed within the forests). The key adaptation caused by this shift in habitat was that our ancestors began to walk on two legs (bipedalism), probably to reduce the surface area exposed to the sun. This left the hands free to do other things, aiding the development of stone tools, which could be used to scavenge and butcher meat, which in turn provided energy for bigger brains. Without that change in the global climate, it is fair to suggest that we might not have become the species we are today.

Human evolution continued to be highly influenced by the environment over the next 5 million years, but this changed dramatically around 2 million years ago when our evolutionary ancestor, a species called Homo ergaster, first started to significantly manipulate its environment. Over the last 2 million years we have been gradually lessening the hold that climate has on us, but never removing it. The extinction of the Neanderthals around 30,000 years ago seems to have been closely related to climate change. Our own species, Homo sapiens, has been able to populate almost every area of the planet; using technology to exploit areas our biological make-up would not be able to cope with.

The process has now come full circle: the environment had a massive impact on our evolution, we evolved strategies to reduce this impact, but these technological innovations have now caused the environment to start moving beyond our control once again. The lessons from our evolutionary past are very clear; humans are part of the environment, not masters of it.

Race Against Time

21/12/2012

Evolution isn’t making people in different parts of the world more distinct. There are no human races, just the one species: Homo sapiens

Originally published by the Guardian 12th December 2007

http://www.guardian.co.uk/profile/simonunderdown

Race is one of the most misunderstood terms in modern science, misused by seasoned scientists and laymen alike. Put simply, there are no human races, just the one species: homo sapiens. The idea of human races is a totally artificial concept, a sloppy form of shorthand that refers to an ill-defined mish-mash of surface differences, such as skin colour (probably controlled by a small number of genes), as well as different cultural practices, especially religious ones. Humans have an innate need to define and categorise, but race is a dangerous and outmoded idea that just can’t keep up with modern science.

The concept of different human races is an old one. From the 19th century onwards, Darwinian ideas of natural selection were misused to justify erroneous concepts of Victorian racial superiority and nationalism. To still talk about separate human races in the 21st century is at best misguided and at worst woefully ignorant of biology.

Our own species is remarkable for our lack of genetic variation. The eruption of the supervolcano Toba approximately 74,000 years ago is thought to have wiped out much of our genetic diversity by causing the extinction of many human groups. All of the differences that we now see in humans are a mixture of small genetic variations, built up over time, and of environmental effects. The Masai Mara and the Inuit have almost identical genes but the differences in their environment have greatly influenced how those genes are expressed, producing different outward appearances.

Yet a recent study continues to prop up this sick old man of biology, suggesting that “human races” in different parts of the world are becoming genetically more distinct. The fact that we are one species does not mean that we should not expect variation between populations, especially ones separated by large distances. Differences do exist, but the shared similarities are far greater. We all remain homo sapiens but the outward and genetic differences we see between populations are retained because of sexual selection and allegorical mating, the simple concept that like attracts like. Similarly the idea that we will all end up looking the same given long enough time is just as flawed as the idea of human races.

The study of human evolution has done much to show up the fallacy of separate human races. Indeed when we examine the work carried out on DNA from Neanderthal fossils (a separate species) huge areas of shared genetic information emerge, not least the FOXP2 or “speech” gene which is identical in humans and Neanderthals. If such little variation exists between two species that last shared a common ancestor over 500,000 years ago, then how comfortable can we be with the idea of separate human races today? Surely it is at last time to put away the idea of different races, celebrate our cultural differences and warmly embrace what makes us all Homo sapiens.

The World from Beginnings to 4000BCE

21/12/2012

The World from Beginnings to 4000BCE (The New Oxford World History)

By Ian Tattersall

Oxford University Press, 160pp, £35.99 and £10.99

ISBN 978-0-19-516712-2 and 978-0-19-533315-2

Published 14 February 2008

Review originally published in the Times Higher 22nd May 2008

Human evolution and astrophysics share more than might be obvious at first glance – both address the ‘big’ questions about existence, both fascinate the non-specialist while appearing bewilderingly complex and self-contradictory.  Bill Bryson in his excellent “Short History of Nearly Everything” says that he was ready to be befuddled by astrophysics but the area of science that took him by surprise by its difficulty was human evolution.  The plethora of popular-science titles available on the subject shows the enduring appeal of human evolution, but of course quantity does not equal quality.  Many books suffer from an over tendency to deal with the human evolutionary process as a simple story – which suggests an inevitability about ‘us’ which is unwarranted given our understanding of Darwinian evolution.  To do otherwise requires a deft touch and the confidence to tackle such a complex area head on – on his past record Ian Tattersall has both in abundance.  Tattersall is one of the grandees of the human evolutionary world and any new book by him demands attention.  The stated aim of this new series of books published by the OUP is to provide an informed, lively and up-to date view of the world that differs from ‘old’ world histories.  How then does this title match up to the stated aims of the series?

Tattersall’s “The World from Beginnings to 4000BCE” is a big book that covers a mere 143 pages.  Starting with the appearance of our most distant ancestors around 7 million years ago it takes the reader through the major evolutionary developments, always pausing to explain how we know what we know and why it’s important.  Ultimately our understanding of human evolution is rather like a patchwork blanket, small pieces of information, taken from fossils, genetics, geology, archaeology etc., are stitched together to produce something greater than the sum of its parts.  It would be easy to fail to convey how and why this is central to the subject but Tattersall deftly avoids this pitfall.  The end product is a comprehensive, yet accessible, review of the current state of human evolution.

This book is not flawless and a major failing is the attempt to take this new history up to 4000 BCE, when in reality the last 6000 years are given a mere 16 pages – an entire volume covering this period would have made more logical sense and better laid the foundations for the rest of the series – this is of course an editorial misjudgement rather than a slight on the treatment Tattersall gives to this period which is as ever balanced and well thought out.  The section containing websites is as something of a Curate’s egg – while they remain active all is good, but the dynamism of the web means that broken links occur with incredible speed.  Likewise the further reading section is comprehensive but the omission of Roger Lewin and Robert Foley’s excellent “Principles of Human Evolution”, unequivocally the next step for the interested reader, is a curious oversight.

Ultimately how good is this book?  Pleasingly, the answer is very.  It takes a complex subject and produces a gripping read while covering the major themes of human evolution with a confidence that is refreshing and will allow the reader to put down the book safe in the knowledge that they have been treated to a master-class in the current understanding of human evolution.

The Social Anthropology of Human Origins

21/12/2012

Social Anthropology and Human Origins By Alan Barnard Cambridge University Press, 182pp, £48.00 ISBN: 9780521765312 Published March 2011

Review originally published in the Times Higher, 14th April 2011

The study of human origins has, apparently, a big problem. A massive unspoken problem, lurking like a veritable herd of elephants in the room. Or to use a metaphor more appropriate to Alan Barnard’s ‘Social Anthropology and Human Origins’, a cowering social anthropologist under the bed. Except when the problem is analysed the only issue with human origins is that a social anthropologist thinks that it should have more social anthropology in it (find me a subject area that doesn’t apply to!). Barnard’s aim is to start a discussion about the role that social anthropology should play in human origins. He suggests that as the largest sub-group of the discipline it should be a relatively simple task to shine the light of social anthropology on our evolution to correct the errors made by all those cold, clinical scientists. As a final coup de gråce, after a very selective review of some of the more recent human evolutionary literature, he concludes that we need to reclassify human origins as a sub-field of social anthropology. Please excuse me if I don’t jump up and shout hooray this suggestion, but at the same time don’t think I have an axe to grind with social anthropology – as part of the RAI team I’ve worked on designing an anthropology A-level which combines both social and biological themes to celebrate what we share as a subject while enjoying the differences of opinion and approach. Barnard argues that the traditional methods employed by biological anthropologists are not good enough to explain our evolution, as they do not take in to account the social or cultural aspects of our evolutionary journey. I find myself at loss to reconcile this statement and others like it with the subject I am part of. The study of human origins is no longer the preserve of ‘us’ biological anthropologists: we collaborate with geneticists, climate scientists, primatologists and archaeologists and ecologists to do just that.

Barnard’s approach is to suggest that the application of lessons learned from social anthropology could improve the depth of human origins as a field. A laudable intention, but with a fatally limited scope which Barnard inadvertently points out at the end of chapter three when he states that social anthropology can not really offer anything for the study of species other than Homo sapiens – and of course we only form only a small part of the evolutionary story of hominins.

This book and the thesis it presents unwittingly portrays social anthropology as a subject that is crying out from the wilderness in search of modern day relevance – yet nothing could be further from the truth. Anthropology is a vibrant subject that has multiple applications across a wide spectrum. The lack, or perceived lack, of social anthropological ideas in human origins is the product of the nature of social anthropological study, based as it is on the often solo participant observation method of study. While this is a point that Barnard concedes it really only makes the conclusion of his book all the more galling for the huge range of scientists working in the field of human origins

The Evolution of Human Cognition

05/10/2012

This term I’ve started teaching a new module ‘Cognitive Evolution’ with my colleague Dr Sam Smith. We’re only two weeks into the start of the term but already it’s throwing up some really interesting questions about why Homo sapiens have such large brains. Not just a little bit big, but really really big! If you compare the primates to all other mammals then they emerge as being ‘brainier’ but then when you look inside the primate order it’s the genus Homo that really start to look like an outlying group. When you look within the genus there are roughly four species that start to follow the pattern of having big brains and display ‘advanced’ behaviours (namely Homo ergaster, Homo heidelbergensis, Homo neanderthalensis and Homo sapiens).  It can be so easy to see this as an inevitable pattern of bigger = better.  Brains get bigger and technology becomes better etc. But the archaeology does not directly correlate with the fossil data – for instance Homo ergaster continued to use Mode 1 tools for about 400,000 years before developing Mode 2 Tools despite having a brain almost twice as large as Australopithecus (Homo) habilis the ‘first; stone tool maker.

Selective pressures are really hard to identify in the fossil record and it notoriously easy to create a misleading narrative (we humans do love a pattern) when looking at human evolutionary themes.  In other words just because we have big brains and use them to do lots of whizzy things today that’s not the same thing as understanding why they evolved. That’s whats so frustrating – the reason our brains are so large is one of the key questions facing palaeoanthropologists but why they did evolve is so hard to fathom. The selective pressures must have been immense to have evolved such a large and energy consuming organ.  Big brains need energy, ours consumes roughly 22% of our daily calorific needs – for natural selection to have produced this state the evolutionary need must have been huge since regular access to high calorie food resources would have been vital for survival.  As ever with human evolution there are a number of competing theories – some argue that our brains have evolved to allow for ever increasing social complexity, while others point towards the relationship between brain size and technological complexity. I lean towards manipulation as one of the key drivers of selection for bigger and bigger brains in Homo.  This ‘lying, cheating and stealing’ model might not be the most uplifting of thoughts but certainly fits with our behaviour as a species.