Ancestral tales: why we prefer fables to fact for human evolution

It seems that barely a month goes by without there being a news article concerning human ancestry. In the eight years since I wrote a post on the apparent dearth of funding in hominin palaeontology there appears to have been some uptake in the amount of research in the field. This is all to the good of course, but what is surprising is that much of the non-specialist journalism - and therefore public opinion - is still riddled with fundamental flaws concerning both our origins and evolution in general.

It also seems that our traditional views of humanity's position in the cosmos is often the source of the errors. It's one thing to make such howlers as the BBC News website did some years' back, in which they claimed chimpanzees were direct human ancestors, but there are a key number of more subtle errors that are repeated time and again. What's interesting is that in order to explain evolution by natural selection, words and phrases have become imbued with incorrect meaning or in some cases, just a slight shift of emphasis. Either way, it seems that evolutionary ideas have been tacked onto existing cultural baggage and in the process, failed to explain the intended theories; personal and socio-political truths have triumphed over objective truth, as Neil deGrasse Tyson might say.

1) As evolutionary biologist Stephen Jay Gould use to constantly point out, the tree of life is like the branches of a bush, not a ladder of linear progression. It's still fairly common to see the phrase 'missing link' applied to our ancestry, among others; I even saw David Attenborough mention it in a tv series about three years' ago. A recent news article described - as if in surprise - that there were at least three species of hominins living in Africa during the past few million years, at the same time and in overlapping regions too. Even college textbooks use it - albeit in quotation marks - among a plethora of other phrases that were once valid, so perhaps it isn't surprising that popular publications continue to use them without qualification.

Evolution isn't a simple, one-way journey through space and time from ancestors to descendants: separate but contemporaneous child species can arise via geographical isolation and then migrate to a common location, all while their parent species continues to exist. An example today would be the lesser black-backed and herring gulls of the Arctic circle, which is either a single, variable species or two clearly distinct species, depending where you look within its range.

It might seem obvious, but species also migrate and then their descendants return to the ancestral homeland; the earliest apes evolved in Africa and then migrated to south-east Asia, some evolving into the ancestors of gibbons and orangutan while others returned to Africa to become the ancestors of gorillas and chimpanzees. One probable culprit of the linear progression model is that some of the examples chosen to teach evolution such as the horse have few branches in their ancestry, giving the false impression of a ladder in which a descendant species always replaces an earlier one.

2) What defines a species is also much misunderstood. The standard description doesn't do any favours in disentangling human evolution; this is where Richard Dawkins' oft-repeated phrase 'the tyranny of the discontinuous mind' comes into play. Examine a range of diagrams for our family tree and you'll find distinct variations, with certain species sometimes being shown as direct ancestors and sometimes as cousins on extinct branches.

If Homo heidelbergensis is the main root stock of modern humans but some of us have small amounts of Neanderthal and/or Denisovan DNA, then do all three qualify as direct ancestors of modern humans? Just where do you draw the line, bearing in mind every generation could breed with both the one before and after? Even with rapid speciation events between long periods of limited variability (A.K.A. punctuated equilibrium) there is no clear cut-off point separating us from them. Yet it's very rare to see Neanderthals labelled as Homo sapiens neanderthalensis and much more common to see them listed as Homo neanderthalensis, implying a wholly separate species.

Are the religious beliefs and easy-to-digest just-so stories blinding us to the complex, muddled background of our origins? Obviously, the word 'race' has profoundly negative connotations these days, with old-school human variation now known to be plain wrong. For example, there's greater genetic variation in the present-day sub-Saharan African population than in the rest of the world combined, thanks to it being the homeland of all hominin species and the out-of-Africa migrations of modern humans occurring relatively recently.

We should also consider that species can be separated by behaviour, not just obvious physical differences. Something as simple as the different pitches of mating calls separate some frog species, with scientific experiments proving that the animals can be fooled by artificially changing the pitch. Also, just because species appear physically similar doesn't necessarily mean an evolutionary close relationship: humans and all other vertebrates are far closer to spiny sea urchins and knobbly sea cucumbers than they are to any land invertebrates such as the insects.

3) Since the Industrial Revolution, societies - at least in the West - have become obsessed with growth, progress and advance. This bias has clearly affected the popular conception that evolution always leads to improvements, along the lines of faster cheetahs to catch more nimble gazelles and 'survival of the fittest'. Books speak of our epoch as the Age of Mammals, when by most important criteria we live in the era of microbes; just think of the oxygen-generating cyanobacteria. Many diagrams of evolutionary trees place humans on the central axis and/or at the pinnacle, as if we were destined to be the best thing that over three billion years of natural selection could achieve. Of course, this is no better than what many religions have said, whereby humans are the end goal of the creator and the planet is ours to exploit and despoil as we like (let's face it, for a large proportion of our existence, modern Homo sapiens was clearly less well adapted to glacial conditions than the Neanderthals).

Above all, these charts give the impression of a clear direction for evolution with mammals as the core animal branch. Popular accounts still describe our distant ancestors, the synapsids, as the 'mammal-like reptiles', even though they evolved from a common ancestor of reptiles, not from reptiles per se. Even if this is purely due to lazy copying from old sources rather than fact-checking, doesn't it belie the main point of the publication? Few general-audience articles admit that all of the earliest dinosaurs were bipedal, presumably because we would like to conflate standing on two legs with more intelligent or 'advanced' (a tricky word to use in a strict evolutionary sense) lineages.

The old ladder of fish-amphibian-reptile/bird-mammal still hangs over us and we seem unwilling to admit to extinct groups (technically called clades) that break our neat patterns. Incidentally, for the past 100 million years or so, about half of all vertebrate species have been teleost fish - so much for the Age of Mammals! No-one would describe the immensely successful but long-extinct trilobites as just being 'pill bug-like marine beetles' or similar, yet when it comes to humans, we have a definite sore spot. There is a deep psychological need to have an obvious series of ever-more sophisticated ancestors paving the way for us.

What many people don't realise is that organisms frequently evolve both physical and behavioural attributes that are subsequently lost and possibly later regained. Some have devolved into far simpler forms, frequently becoming parasites. Viruses are themselves a simplified life form, unable to reproduce without a high-jacked cell doing the work for them; no-one could accuse them of not being highly successful - as we are currently finding out to our cost. We ourselves are highly adaptable generalists, but on a component-by-component level it would appear that only our brains make us as successful as we are. Let's face it, physically we're not up to much: even cephalopods such as squid and octopus have a form of camera eye that is superior to that of all vertebrates.

Even a cursory glance at the natural history of life, using scientific disciplines as disparate as palaeontology and comparative DNA analysis, shows that some lineages proved so successful that their outward physiology has changed very little. Today, there are over thirty species of lancelet that are placed at the base of the chordates and therefore closely related to the ancestors of all vertebrates. They are also extremely similar in appearance to 530-million-year-old fossils of the earliest chordates in the Cambrian period. If evolution were a one-way ticket to progress, why have they not long since been replaced by later, more sophisticated organisms?

4) We appear to conflate success simply with being in existence today, yet our species is a newcomer and barely out of the cradle compared to some old-timers. We recently learned that Neanderthals wove plant fibre to make string and ate a wide variety of seafood. This knowledge brings with it a dwindling uniqueness for modern Homo sapiens. The frequently given explanation of our superiority over our extinct cousins is simply that they aren't around anymore, except as minor components of our genome. But this is a tautology: they are inferior because they are extinct and therefore an evolutionary dead end; yet they became extinct because of their inferiority. Hmmm...there's not much science going on here!

The usual story until recently was that at some point (often centred around 40,000-50,000 years ago) archaic sapiens developed modern human behaviour, principally in the form of imaginative, symbolic thinking. This of course ignores the (admittedly tentative) archaeological evidence of Neanderthal cave-painting, jewelry and ritual, all of which are supposed to be evidence of our direct ancestor's unique Great Leap Forward (yes, it was named after Chairman Mao's plan). Not only did Neanderthals have this symbolic behaviour, they appear to have developed it independently of genetically-modern humans. This is a complete about-turn from the previous position of them being nothing more than poor copyists.

There are alternative hypotheses to the Great Leap Forward, including:

1. Founder of the Comparative Cognition Project and primate researcher Sarah Boysen observed that chimpanzees can create new methods for problem solving and processing information. Therefore, a gradual accumulation of cognitive abilities and behavioural traits over many millennia - and partially inherited from earlier species - may have reached a tipping point. 
2. Some geneticists consider there to have been a sudden paradigm shift caused by a mutation of the FOXP2 gene, leading to sophisticated language and all that it entails.
3. Other researchers consider that once a certain population size and density was achieved, complex interactions between individuals led the way to modern behaviour. 
4. A better diet, principally in the form of larger amounts of cooked meat, led to increased cognition. 

In some ways, all of these are partly speculative and as is often the case we may eventually find that a combination of these plus other factors were involved. This shouldn't stop us from realising how poor the communication of evolutionary theories still is and how many misconceptions exist, with the complex truth obscured by our need to feel special and to tell simple stories that rarely convey the amazing evolution of life on Earth.

Ancestral claims: why has there been comparatively little research into human origins?

It has been said that we live in a golden age of dinosaur discoveries: from Liaoning Province in China to the Dakota Badlands, new species are being named on an almost monthly basis. But if there is a plethora of dinosaur palaeontologists why has there seemingly been so few scientists studying the origin of Homo sapiens? Surely deciphering the ancestry of mankind is one of the great challenges?

The image of hominins has certainly evolved over the past thirty years, even the naming changing in scientific circles (from the broader term hominid), although as the title of the 2003 BBC series' Walking With Cavemen showed, popular perception has been slow to adopt new research. As a child, I had an early 1970s plastic model kit of a Neanderthal Man. I seem to recall it bore more than a passing resemblance to the Morlocks from the 1960 film adaptation of H.G. Wells's The Time Machine, a far cry from the individuals portrayed in Walking With Cavemen and other, more recent, series. Yet this idea of a shambling, zombie-like creature is still to some extent prevalent. Why should this be, when there is now evidence for Neanderthal ritual and art? Are we simply afraid of finding yet more nails in the coffin of human uniqueness (apologies for the rusty metaphor)?

There are still clear elements of taboo to the subject: the humbling  notion of humans being but a 'monkey shaved' was also felt by early evolutionists, with even natural selection co-founder Alfred Russel Wallace believing humanity the product of divine fiat. Perhaps a sense of embarrassment (try watching zoo visitors as they observe apes) combined with Western religious thought has prevented the discipline becoming popular in the way the love of all things dinosaur has skyrocketed since the 1970s.

Then again, it still seems that people misunderstand evolution via natural selection, considering progress as via ladders rather than differentiating bushes. The 2004 discovery of yet another new hominin species, Sahelanthropus tchadensis, led the Christian Science Monitor to describe it as that hoary old misnomer the 'missing link'. This is despite three decades of popularising by the likes of Dawkins, Fortey, Jay Gould, etal, to dispel the notion. You only have to read archaeologist (note: not palaeontologist) Mark Roberts’ account of the seemingly shoestring Homo heidelbergensis excavations at Boxgrove in England to realise that hominin research has been attracting about one per cent of the news (and a zillionth of the funds) directed towards cutting-edge particle physics.

A primary cause for the dearth of public knowledge can be put down to the actual lack of direct fossil evidence. Although Neanderthal remains were the first actually recognised as belonging to a human ancestor, it took several decades after the initial 1829 discovery before the identification was scientifically confirmed. Into the Twentieth Century the lack of finds allowed such embarrassments as the poor-quality Piltdown fake to be taken at face value. It is easy to see at least one key reason why this should be: human ancestry carries so much emotional baggage that it took over forty years before British scientists saw the obvious, instead of following the patriotism and jingoism inspired by the finds.

As it is, the history of hominin palaeontology has been riddled with contention, serendipity, unfortunate accidents and amateur bungling. If anyone wants to disprove the myth of science as a sterile, laboratory-conditioned activity, this sphere provides key evidence par excellence (good to get a rhythm going). From Eugene Dubois hiding his Java Man (Homo erectus) remains for several decades early in the Twentieth Century to the disappearance of Peking Man (also Homo erectus) fossils during the Second World War - not to mention the grinding up of yet more erectus bones for Chinese traditional medicine - the fate of finds is enough to make a dedicated specialist weep.

In addition, the fact that humans and their ancestors primarily evolved in what are today remote African locations with limited infrastructure can only exacerbate the situation. The work can be tedious, physically arduous and rewards few and far between. Yet fossil remains are the backbone of the discipline (almost a pun there, if you really look for it). After all, an increase in the number of finds can also lead to a paradigm shift in understanding: in the last few years it has been possible to undermine the opinion given on the BBC documentary The making of Walking with Dinosaurs, first broadcast back in 2000, that we would never know the colour of any dinosaur, courtesy of feathered Chinese theropod fossils (try saying that three times fast).

However, the last few decades has seen an improvement in the number of finds as funding has been allocated and professional enthusiasm increased. The problem has been that rather than solidifying the story of our ancestral line the number of species has multiplied without aiding the overall picture; there are still plenty of dashed lines on the human family tree. This indeterminacy has meant that a consensus is hard to find. If you examine any two charts of human ancestry, the chances are that they won’t agree. In the face of limited evidence it seems relatively easy for palaeoanthropologists to promote their own theories as to which species are our direct ancestors. Human nature being what it is, the favoured species usually happen to be those discovered by the said promoter. Such behaviour led to a thirty-year rift between two of the key players, Richard Leakey and Donald Johanson, partially over the number of branches on the direct ancestral tree. If anyone thinks the days of feuding scientists as long past (consider for example the Nineteenth Century American dinosaur pioneers Cope and Marsh) this quarrel ought to set the record straight.

One area of research that has undoubtedly given a boost to the understanding of human origins is the ability to retrieve and read ancient DNA. That’s not to say that it has yet produced much in the way of definitive evidence, but it undoubtedly widens the knowledge that can be gained from a paucity of finds. A recent report suggested that Homo sapiens and Neanderthals did not after all interbreed but share a similar genome via common ancestry. This is a reversal of a previous report that in turn countered earlier genetic evidence...and so on.

The relatively recent demise of the Neanderthals has provoked some interesting theories that show how science can reflect the concerns of contemporary society, namely that the violent aspect our species may have been directly responsible. There is currently no firm evidence for deliberate genocide, with other likely culprits ranging from inability to adjust to climate change to a less flexible neural architecture (specifically, missing out on the 'Great Leap Forward' via imaginative cogitation). Recent texts have attempted to downplay innate human aggression but writers closer in time to the world wars and to the heyday of Freudianism, especially Australian anthropologist Raymond Dart and American author Robert Ardrey, had a major influence on the subject with their promotion of the 'killer ape' theory. From 1960 onwards the first serious, sustained research on wild chimpanzees by Jane Goodall inadvertently reinforced the notion of mankind as a predominantly violent species. Given such notions, it is perhaps little wonder that funding has been lacking.

The new century has so far seen something of an improvement, with a large increase in the number of popular books and television programmes reflecting and in turn further developing public interest. The controversy surrounding the nature of the Homo floresiensis finds of 2003 has proved fortuitous, with general news media at long last paying serious attention. The ball may have been started rolling by the Chalcolithic ice mummy Otzi, who was discovered in the Alps in 1991. A young upstart at a mere 5,300 years old, the incredible preservation of the man, his clothing and tools have helped bridge the gap in how we relate to our prehistoric ancestors.

So times they are a-changing. The Ancient Human Occupation of Britain project is a sustained, well-funded effort to examine the past 700,000 years of evidence in the United Kingdom using a plethora of cross-discipline techniques in addition to conventional archaeology and palaeontology. The use of advanced dating methods such as electron spin resonance and the ability to analyse ancient DNA suggest that even without new finds, hominin research in the near future will generate some surprises. All I can say is that it's about time, too!