Hominin Evolution Book Review: Bones of Contention (1987)

It has been a while since I posted on my blog and so out of guilt I’m back again to give you all a new post. This time I want to review a book published in 1987 on the political history of Palaeoanthropology. Written by biochemist Roger Lewin (1944 – Present) it charts the history of the science of Palaeoanthropology and is a must read for anyone interested in the origins of the genus Homo. In 1989, Lewin won the Royal Society Prizes for Science Books, for this very work. Many palaeoanthropologists at the top today could use with reading this book, to help them reflect on their own interaction with other workers in the field. The book was later revised in 1997, which at the time of posting was 21 years ago. There is no question that the field in need of an update to see if the field has changed or remained the same. I hope we will see this 3rd edition in the near future. Among other topics there is no doubt that the recent sexual misconduct of some scientists will need to be discussed in that new book. Let’s talk about the book. The title is very appropriate but when I first heard of it many years ago, I couldn’t help but bring out the immature side in me and snigger at the close similarity of the title with “Boners of Contentions”.  I pondered on the potential look of the T-shirt, I could have printed. Anyway, the book covers a number of important moments in palaeoanthropological history.

In no particular order, Lewin discusses the storm surrounding the Taung Child, Ramapithecus, the KBS Tuff, the famous Australopithecus afarensis A.L. 288-1 and finally the work of the Leakey, specifically the father and the son. Here we see human nature at its worst usually, particularly when we get emotionally invested in a fossil or hypothesis or even flawed radiometric dating. Human evolutionary research, whether the workers in the field, like it or not, is storytelling. Storytelling based on evidence, I might add, but it possesses shades of science fiction. The hominin fossil record is extremely fragmentary and the stories told by these fossils are also extremely fragmentary. They are necessarily weak and this is not particularly useful in a field, where the scientists develop emotional attachment to their pet hypotheses. Even in the light of new evidence many still ignore due to the embarrassment of admitting you are wrong, based on the new evidence. In Palaeoanthropology, admitting you were wrong has been virtually impossible. There is really only one recorded case of a straight up “I was wrong and someone else was right”, that honour goes to Arthur Keith and his review of Raymond Darts Taung Child.

The book allows me to reflect on my own strongly held convictions that Homo heidelbergensis is a valid taxon, at a time when palaeoanthropologists generally shy away from using it. I have imbued it with my own emotional attachment and will remain unconvinced that it should be invalidated. But equally, those who argue the latter, are blinded by their own biases. They do forget that the fossil record of the species is incredibly sparse, with only a handful of skulls representing it. Admittedly, they have a point regarding the Mauer Mandible as the holotype of the species. Ideally, the holotype should be a complete skeleton, but the early science of palaeoanthroplogy was not rigorous in how it proposed new species. So, we are stuck with a mandible in a hypodigm entirely of crania, you read right one mandible and a handful of crania. This, I would argue is no grounds to invalidate a species. In debates, the emotional investment, gets in the way of objective thought and they can get quite heated. Thankfully, I’m not the only palaeoanthropology student indulging in Pro-Heidelbergensis camp. In 2017, Roksandic et al., conducted a revision of the representatives of Homo heidelbergensis. Bones of Contention has allowed me to at the very least be aware of my flaws when it comes to interpreting the fossil record, but with the above paragraph, I’ve really only scratched the surface and it will require a separate essay on the topic for the future.

Bones of Contention is a well written book and while it loosely follows event chronologically, Lewin does compare and contrast most of the events, concluding with a theme that binds these momentous events together. The reminder that we are telling stories is the key thought all palaeoanthropologists should be aware of. I’m aware that the latter is quite a risky statement, but in order for the palaeoanthropology student to be as objective as possible, we need to keep reminding ourselves of that. Many at the top, I suspect, will laugh at this as obsurd. One could argue that the science is far more rigorous in every way today than the time Eoanthropus dawsonii was first unveiled to the world. The Humans that study the fossils, well they have not changed. We are still flawed scientists, whether we like to admit it or not. This is uncomfortable for me to say, but it is true. In the early 1900’s, scientists saw hominin evolution as a variation of the chain of being, a line from ancient apes to human’s, today a variation of multiregional evolutionism is the hip new hypothesis with the “river delta” as its logo.

One topic that the book does not cover is the nature of public engagement of palaeoanthropology contrasted with scientific process associated with palaeoanthropology. For me, these are two different worlds, incredibly incompatible and one scoffs at the other in righteous indignation. There will be no way to bridge the gap between the two. Yes, some seem to be bridging this gap, but if you really dig deeper, the reality is very different. Science is an ever shifting process of evidence evaluation, something that is incompatible with the requirement of certainty in the press. I often cringe at the often used phrase that “textbooks will have to be re-written on palaeoanthropology”. This comes as no surprise to any palaeoanthropology student, but this statement implies that palaeoanthropologists had figured out the evolutionary steps hominins took over the past seven million years to get to where we are today. Far from it and this is what angers a lot of palaeoanthropology students and lecturers. The media need a hook and unfortunately the most effective hook to draw the public in is the above statement. You can’t blame them for reaching as wide an audience as possible. But this has meant that palaeoanthropologists in particular are cautious when they engage with the media. The seemingly innocuous move to record conference talks on new scientific findings is very risky from the point of view of the speaker. Choice of words at a presentation on record and the choice of words on the academic paper may be subtly different but they have the potential to ruin the academic standing of the speaker. Additionally, journals have strict embargo rules on when engagement with the media can begin. Break these rules and the paper will never be published. There will remain a tension between these two worlds for many centuries to come. I hope that the 3rd edition of Bones of Contention will cover this in more detail than I have here.

The only criticism I have of the book is the placement of the black and white photographs in the book. It would be more beneficial to have them scattered throughout the book, associated with their appropriate chapters, instead of combining them together  in two groups in the centre of the book. This is not much of a criticism, but it does demonstrate the difficulty I had in my attempt to find one. It is an excellent book. To use a quote from Leonard to Sheldon in the Big Bang Theory, reading this book “is like looking into an obnoxious little mirror”. It help us re-examine ourselves and re-focuses our thoughts on a very controversial science.

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Three reasons the Cerutti Mastodon was not manipulated by hominins

A team of scientists recently announced an extraordinary claim that the 130,000 Cerutti Mastodon was manipulated by hominins.

“I have read that paper and I was astonished by it,” archaeologist Donald Grayson of the University of Washington. “I was astonished not because it is so good, but because it is so bad. Cracked bones and chipped stones at a fossil site might mean anything”, said Grayson. “It is quite another thing to show that people, and people alone, could have produced those modifications. The study doesn’t take that step, he said, “making this a very easy claim to dismiss.”

Gary Haynes of the University of Nevada Reno had this to say, “The paper states that the bones were being exposed by a backhoe. These pieces of heavy equipment weigh seven to fifteen tons or more, and their weight on the sediments would have crushed bones and rocks against each other.” When asked, Holen, the study leader, said that it “was very easy to tell the difference” between fractures made by stone hammers and those seen in bones crushed by bulldozers. He did not elaborate on how the differences manifest. “He’s pretty much dead wrong — there’s no definable difference,” Haynes said. A similar fossil dispute broke out in 2015 over a 24,000 year old mammoth in Maryland, he noted, shown to be fractured by heavy equipment. Also troubling, the “hammer” and “anvil” stones described in the paper don’t unequivocally look like tools, said Michael Waters of Texas A&M’s Center for the Study of the First Americans.

Michael Waters of Texas A&M’s Center for the Study of the First Americans noted that the “hammer” and “anvil” stones described in the paper don’t unequivocally look like tools. The study also runs afoul of the mounting genetic evidence, which indicates that the first people to reach the Americas and eventually give rise to modern Native Americans arrived no earlier than 25,000 years ago.”

The First Human Epidemic: Late Pleistocene Origin?

Current models of infectious disease in the Pleistocene tell us little about the pathogens that would have infected Neanderthals (Homo neanderthalensis). High quality Altai Neanderthal and Denisovan genomes are revealing which regions of archaic hominin DNA have persisted in the modern human genome. A number of these regions are associated with response to infection and immunity, with a suggestion that derived Neanderthal alleles found in modern Europeans and East Asians may be associated with autoimmunity. Independent sources of DNA-based evidence allow a re-evaluation of the nature and timing of the first epidemiologic transition. The paradigm of the first epidemiologic transmission, the hypothesis that epidemic disease did not occur until the transition to agriculture, with larger, denser and more sedentary populations, has been essentially unchallenged since the 1970s. Our views of the infectious disease environment of the Pleistocene period are heavily influenced by skeletal data and studies of contemporary hunter-gatherers. New genetic data – encompassing both hosts and pathogens – has the power to transform our view of the infectious disease landscape experienced by Neanderthals in Europe, and the anatomically modern humans (AMH) with whom they came into contact. The Pleistocene hominin environment cannot be thought of as free from infectious disease. It seems likely that the first epidemiologic transition, envisaged as part of the package of the Holocene farming lifestyle, may be fundamentally different in pace or scope than has previously been suggested. This paper demonstrates how high quality genomic data sets can be used to address questions arisingfrom the ecological context that shaped the co-evolutionary relationship we share with infectious diseases. We analyse the evidence for infectious disease in Neanderthals, beginning with that of infection-related skeletal pathologies in the archaeological record, and then consider the role of infection in hominin evolution. We have synthesised current models on the chronology of emergence of notable European disease packages and analyse what implications this evidence has for the classical model of the first epidemiologic transition. Using emerging data from Neanderthal palaeogenomics and combining this with fossil and archaeological information we re-examine the impact of infectious diseases on human populations from an evolutionary context. These palaeogeneticists argue that the first epidemiologic transition in Eurasia was not as tightly tied to the onset of the Holocene as has previously been assumed. There is clear evidence to suggest that this transition began before the appearance of agriculture and occurred over a timescale of tens of thousands of years. We suggest that the epidemiological transition was not, as has been thought since the 1970s, a phenomenon of the human shift to sedentary agriculture during the Holocene but a much older and more complex process that involved at least two species of humans. The origin of resistance to infectious disease has a much deeper timeframe and is highlighted by the ingression of Neanderthal DNA into modern human lineages. The transfer of pathogens between human species may also have played a role in the extinction of the Neanderthals. Our analysis of the genomes of archaic hominins provides evidence of pathogens acting as a population-level selection pressure, causing changes in genomes that were passed on to descendants and preserved in the genomes of modern Eurasians. the analysis of ancient genomes demonstrates that human behavioural patterns (in this case a shift to agricultural subsistence) should not be used as an ecological proxy to explain shifting trends in the co-evolutionary relationship between pathogens and human populations.

This work is available on BioRxiv: http://dx.doi.org/10.1101/017343

Acknowledgements: Rob Foley, Marta Lahr and the members of the Human Evolutionary Science Discussion Group at the University
of Cambridge. Funding for this research was provided by King’s College Cambridge and UCL.

Homo floresiensis: Extracting Ancient Deoxyribonucleic Acid (aDNA): It’s Been 4 Years, any success?

I recently came across this scientific article in the Journal of Human Evolution entitled, Ancient DNA Analysis of Dental Calculus by Weyrich et al. It reminded me of the research conducted on the Indonesian hominin, Homo floresiensis. So, here I summarise what we know thus far. Dating to between 95,000 and 17,000 years ago, the hominin was found in the cave of Liang Bua, overlooking the Wae Racang river valley, on the island of Flores. It’s most remarkable feature was the 1.06 m stature of the individual found. Begging the question, how is this hominin related to us and what led to its diminutive stature. Much of the debate was thoroughly summarised in Leslie Aiello’s paper entitled, Five Years of Homo floresiensis, back in 2010. In short, some questioned the validity of naming these individuals a new species of human. Evidence was brought forward to support the hypothesis that these people were suffering from the neurodevelopmental disorder, Microcephaly and other diseases that induce a reduced stature. As time has passed, media sensation abated and researchers had a chance to step back, the majority are now more accepting of the Australian-Indonesian team’s decision to apply the new hominin nomenclature. Much of the debate hinges on skeletal comparisons between Homo floresiensis and other hominins, like us. There is one piece of information that the individuals of Liang Bua have yet to reveal – Deoxyribonucleic Acid.

Kilimutu Crater Lakes, Flores, Indonesia
Kilimutu Crater Lakes, Flores, Indonesia

Two teams of scientists, the Australian Centre for Ancient DNA (ACAD) and the Department of Evolutionary Anthropology at the Max Planck Institute (MPI) attempted and failed to extract DNA from the individual’s teeth in 2006. This was due to the environment in which the hominins were found, which was not conducive to DNA preservation. Christina Adler of ACAD hypothesised that the reason for extraction failure could be due to extraction procedure. In 2007 the ACAD team sucessfully extracted DNA from a pig tooth unearthed at the Liang Bua Cave, which was about 6,000 years old. The team suggested that first, Cementum (calcified root covering) is the richest source of DNA and second, drilling the specimen destroys the very molecule they are after. Armed with this knowledge another attempt to extract DNA from the hominins of Liang Bua is still yet to be carried out. The year 2013, saw the successful extraction of 400,000 year old DNA in Spain, so Floresiensian DNA may still lie within the teeth. I’m hoping, despite the less than ideal high temperatures of the cave sediments, there lies within those hominin individuals such strands of the good stuff.

Cranium and mandible cast of Homo floresiensis individual, LB1
Cranium and mandible cast of Homo floresiensis individual, LB1

Returning to the paper I mentioned at the beginning, it is a summary of all we know regarding the extraction of aDNA and steps to take when extracting it from calculus on teeth. Calculus is a hardened group of micro-organisms that appear as a yellow build-up usually around the gum-tooth boundary. The first demonstration of aDNA in Calculus was documented in a paper entitled Ancient Bacterial DNA (aDNA) in dental calculus from archaeological human remains by Preus et al., in 2011. A year later, aDNA was extracted from Neolithic Argentinian and Chilean humans. In that study, five bacterial species gene sequences were amplified by targeted polymerase chain reactions (PCR). By 2014, Warinner et al., used the power of the metagenomic sequencing strategy demonstrated increased resolution, the identification of antibiotic resistence genes and though the specimens were put through an Ethylenediaminetetraacetic acid (EDTA) and bleach treatments, DNA was recoverable.

Deoxyribonucleic Acid (DNA)
Deoxyribonucleic Acid (DNA)

When analysing hominin diets, microfossils are a large component, but the strides being made in aDNA extraction will mean that the species of plant or animal will be identified or as it usually does, throws up more questions than answers.

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