Another species of human discovered – and what it means for us

I was intrigued by reports last week on the discovery of a previously unknown extinct human species, Homo luzonensis, in a cave in the Phillipines. It’s the fourth new human species – genus Homo – discovered in the past twenty years. All are extinct, and much clearly remains to be revealed, but it’s nonetheless clear that older ideas about the nature of human evolution as a one-species ‘ascent’ are long gone.

That journey of discovery has been a wild ride – one I’ve been following closely. I did the sciences before focusing on history, and one of my undergrad degrees is in anthropology. Back in the early 1980s, when I was at university, human evolution was simple; we’d always been a single species, with maybe a couple of dead-end side branches, now gone, and that was that. Paleo-anthropology consisted of putting the prior forms into the right order. It stood to reason: there were many species of other animal, but only one of human.

By the mid-twentieth century this notion was being quietly questioned in the academy – not least because it implied that humans were exempt from the processes known to apply to everything else when it came to evolution. But the idea was effectively still mainstream even in academic circles. It was popularly given weight through an influential infographic by Rudolph Zallinger, the ‘march of progress’, published by Time-Life in 1966. This became a trope, presenting human evolution as a linear ascent from crouching and primitive ape to upstanding and sophisticated modernity.

Public-domain example of the ‘march of progress’ trope, following Zallinger (1966). It’s long discredited. Note the modern gibbon and chimp at the left of the line (certain politicians may be evolved from them… but I’m not). Public domain, via Wikipedia.

The particular point of debate by the 1980s was over how modern humans had somehow emerged in every part of the planet when there was also evidence of prior forms – such as Homo erectus – across a wide swathe of the globe. Either humans had come ‘out of Africa’ and migrated more than once, each new form supplanting the last. Or there had been parallel evolution. From this emerged ‘multi-regionalism’, which argued that in defiance of the way evolution worked for everything else, isolated erectus populations simultaneously became identical modern humans in different environments, some as diverse as Java and England.

The thing is that modern humans are a single species. Indeed, we’re unusually close, biologically – if we were dogs, we’d be a single breed (labradors, I hope). It indicates there was a population bottleneck in the not-too-distant past, maybe 70,000 years back. This ultra-close relationship within Homo sapiens meant it wasn’t plausible for every H. erectus, everywhere, to have suddenly become an identical form of modern human. And yet evidence for multiple exits from Africa was non-existent at the time.

As a result there was an apocalyptic academic struggle between the ‘out of Africa’ camps and the ‘multi-regionalists’. By the 1980s, paleo-anthropologists were screaming at each other, desperately trying to prove to the world how ignorant and incompetent any colleagues were who followed the ‘other’ theory. Much pivoted on the implicit assumption that humans were a special case, further driven by the fact that, at the time, the total physical evidence of ancestral human species and locations amounted to just a few dozen specimens. The fact that ‘multi-regionalism’ flew in the face of accepted mechanisms of allopatric speciation (to use the technical term) was met by sophistries such as assumed back-migration, none of which had any evidence behind them.

Artists’ reconstruction of H. georgicus, a variant of H. erectus.

Since then those arguments have been put to rest by a flood of new evidence. Humans seem to have emerged in a habitation range stretching from modern Ethiopia perhaps into the Middle East, spreading both out of – and, in a curious reversal of old thinking, in to Africa. It happened multiple times. Humans also speciated like every other animal – meaning that each new form did not replace the old, but that multiple species of human lived simultaneously, shaped by genetic drift and by environmental pressures. And we’re finding the examples. The question is how to understand what’s been discovered. Given what I know about human nature and academia, I can’t help thinking this will trigger yet another shit-fight in the paleo-anthropological community (it’s an ape thing, weaponising one’s own ordure, and the fact that humans do it intellectually rather than literally doesn’t reduce the symbolism).

Holotype specimen of H. naledi, Berger et al, Creative Commons 4.0 license via Wikimedia.

So – it’s clear now that we, H. sapiens, are the last humans out of at least half a dozen species in our family. The very last. Aside from the obvious responsibilities now resting on our shoulders, that begs another question. Why did our species survive, alone of all humans? It’s not, I suspect, because we have anything special. We may not even have been smartest; there’s evidence that Denisovan and Neandertal stone-age tech was better than ours, and they had bigger brains than we do, on average. Remember, Neandertals invented epoxy resin about 40,000 years before we did. They were also physically at least twice as strong as we are.

Homo heidelbergensis, thought to be the ancestor of H. sapiens, Neandertals and Denisovans. They are also known to have built houses and live in small village-like communities. Photo: Jose Luis Martinez Alvarez, Creative Commons 2.0, via Wikimedia Commons.

For all that, old tropes have died hard. For a long time the idea was that the modern body form emerged about 1.5 million years ago with H. erectus and that our evolution after that consisted purely of the relentless expansion of a single body part – and yes, I mean the brain – although nothing else changed. And there was a supposition that eyebrow ridges and low forehead implied stupidity. It’s still widely held outside the science community. The first news I read of the new find, in a general news website, described Neandertals as ‘thick-browed yet sophisticated’. But hey – how did Neandertals think of us? Flat-faced children? H. sapiens adults have the same facial structure as Neandertal kids did, pre-puberty (which came earlier for Neandertals than for us) – and we’re physical weaklings by their standards. The technical term is neotony.

Of course, Neandertals have always had a bad rap, thanks to old social tropes of directional evolution. In this vision, dripping in ethnocentric culturalism, Neandertals were the ‘missing link’ with apes. They spoke in deep grunts, lacked intellect, had names such as Thog, and went extinct for no better reason than that they were stupid and out-competed by Homo sapiens, aka Man The Wise. Apparently.

The notion that Neandertals were just different, like lions are different from tigers, took time to emerge. They lived in ice-age Europe, and their anatomy was well-adapted to cold; their protruding face (technically, ‘prognathic’) meant they had long nostrils to pre-warm the air. Their brains were bigger than ours, and analysis of endo-casts indicates that although differently shaped, they were not less than ours in functionality. In short, Neandertals were just as sophisticated as us in their own way, and perhaps superior. Oh – analysis of their vocal tract and hyoid bone structure implies they probably had high-pitched voices.

But even once this had begun to emerge, the notion that H. sapiens was somehow exceptional among human species remained implicit within the science community. I’ve got a book in my collection, penned by a couple of academics from the University of Colorado, How to think like a Neandertal. They essentially argued that sure, Neandertals were smart, had brains bigger than ours, made clothes, had epoxy resin, and so on. But they were still broadly static and uninventive. The authors suggested the difference was H. sapiens social-group size and abstract creativity, painting a scenario of small Neandertal families sitting huddled around a fire in near-silence, while across the valley the bands of H. sapiens are socialising in large groups, story-telling, singing and so forth. The implication is that Neandertals were not in the league of their more creative cousins and, variously, succumbed to a combination of sapiens’ success and environmental pressures to which they could not adapt swiftly enough.

The thing is that, just now, the long-held paleo-anthropological idea of all humanity living in a kind of intellectual fog, and the light suddenly going on for H. sapiens alone, about 40,000 years ago, is a bit shaky. Since that book was written, archaeologists have found Neandertal-made cave art, jewellery and musical instruments. It’s also been discovered that they threw spears – another thing reserved as an H. sapiens achievement and decisive advantage for hunters. Meanwhile, the story of another close cousin, the Denisovans, is just beginning to unfold. And guess what – their mesolithic tech was also superior to H. sapiens, and they made jewellery – and there’s doubtless more to come.

Still, the idea that H. sapiens is exceptional refuses to die, despite mounting evidence that we’re not. That’s in part because we, alone, survived.  But was this simply accident? The great age of apes was the Miocene, which ended five million years ago. Since then, the number of all ape species have declined sharply. Most are extinct. All that’s left of the so-called ‘great’ apes are one species of human, two of chimp, two of gorilla, and three of orang-utan (one was recently discovered). Time has not been kind to family Hominidae. The behaviours that characterise this family – chimps and humans especially – are not, it seems, a long-term recipe for survival. There is good reason to suppose that our sole surviving human species is around only by chance. Luck, not exceptionalism, left us alone to carry the human torch forwards. Thoughts?

Copyright © Matthew Wright 2019

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17 thoughts on “Another species of human discovered – and what it means for us

  1. Totally agree, Matthew – I think current humans survived by learning from other species of Hominidae, using their ideas, technology, mating with them, mixing their genes with ours, etc, and generally contributing to their demise.
    We also probably reproduced faster, travelled and spread faster, therefore, by sheer good fortune, when disasters occurred, like climate change and resulting staple food shortages, our lot were too widespread to be totally wiped out.
    Regarding the mixing of genetic materials, it’s interesting that Western European’s and Middle Easterners have Neanderthal traces, Eastern and Far Eastern have Denisovan (plus an unknown) traces and Africans have no traces of other hominids (as far as we are aware)
    Neanderthals survived for 300,000 years and Homo Erectus for 250,000 years, so I’d say they were both successful species (certainly not wimps).

    1. The exciting news – just the other week – about the Denisovan admixture in Papua New Guinea is that it appears to have come from two distinct Denisovan groups. Interesting. Our pre-history was a lot more variegated than we perhaps ever imagined. I’d hesitate to suppose it was some kind of great Paleolithic love-fest, though: if inter-breeding had been common, the species distinctions would have disappeared. I have seen reports that not all were fully inter-fertile. They were close, but not that close apparently.

        1. We sure do! What frustrates me is that we can only discover non-perishables at this remove in time; unless there’s something yet buried in permafrost, we can’t really tell how our predecessors and cousin species used skins, wood and so forth. Still, if discoveries continue at the same pace as in recent years, I’ve no doubt we’ll either detail or overturn current thinking. Or both…

    1. And I absolutely respect that. To me even if people have differing views, we are all people and have valid right to believe what we do – and, for my part, I’ll absolutely defend the others’ right to have their views and beliefs, and respect their integrity for standing by those beliefs, whether they accord with mine or not.

  2. Not wishing to step on anyone’s toes, but one has to wonder how much religious beliefs have to do with ethnocentrism. Don’t know how you’d untangle that one, but I’ve always thought that, as you put it, weaponizing one’s ordure via language had more to do with the carryover of religious doctrinal disputes than what scientists should be doing.

    And yes, I realize that’s VERY naive of me. But seriously, in religious terms, if we both have different “revealed” truths, obviously one of us is not merely wrong but also is quite likely heretic and apostate. That’s been a recipe for conflict throughout human history.

    In theory, though, science is about determining the truth, not about a school of thought or “revealed truth” in any way. I’ve always thought coming to conclusions absent sufficient data was a suspicious practice. Undergrads should be taught that scientific knowledge has limits and those limits are liable to serendipitous expansion, which should surprise no one when they occur.

    Perhaps it shouldn’t be surprising. The example of science, barring some few and illustrious exceptions, is perhaps two and a half centuries old. That’s not even an eyeblink in terms of human history, much less broad social comprehension.

    1. Interesting point! It seems to me one of the issues is the fact that human thinking, as mediated by society, tends to swing from ‘moderate’ to ‘more extreme’ views and back. This is particularly so for beliefs that carry a substantial emotional payload, such as religion. Hence religious wars; and those who fight them, I suspect, have usually lost perspective of the original teachings of their religion which – in every case I can think of, Abrahamic or otherwise, revolves around kindness and care for others. (I am a third-generation atheist, but I certainly respect the right of others to hold their own beliefs).

      I think the mind-set of exceptionalism isn’t unique to the western diaspora; Aristotle and Socrates held it, as did the Romans. That then infused itself into our culture, naturally including Christian teachings. Religion was certainly the context of the first efforts to systematise the biological world. Johann Scheuchzer put the place of humanity plainly in his Sacred Physics of 1731: on the sixth day, when God had created the world and all in it, Man appeared, this ‘most noble of creatures’, able finally to arrive once the ‘table is fully spread’, there to take his rightful place as ‘the Ruler of all the works of the hand of God’. Curiously, the issue with Darwin and the Church of England wasn’t quite as it seemed; Archbishop Samuel Wilberforce (‘Soapy Sam’, to his detractors) was given ammunition by Richard Owen, Darwin’s former teacher-turned-enemy. Yup – it was just another rather dreadful academic turf war…

  3. I’ve read that H.Sapiens genetic code contains a fair bit of Neanderthal DNA.
    Is it possible that we simply bred faster and absorbed the Neanderthals?
    Or…nasty thought, did we enslave the females, breed with them and kill off the males because…we were/are xenophobic and aggressive?

    1. Yes it does, in Europe particularly – up to 3 percent apparently. And there was a discovery published just a couple of weeks ago showing that Papua New Guineans have a similar proportion of Denisovan. The kicker is that there seem to have been two distinct Denisovan groups (identified by the genetic analysis) separated by about 150,000 years. Remains have also been found, just this year, of a first-generation Denisovan-Neanderthal cross, again identifiable genetically. All this means that these three species of human, at least, were inter-fertile. However, cross-breeding may not have happened often; if it had, the percentage of each other’s DNA would be much higher. (I’ve seen arguments that, because of the genetic differences, Neandertal men could breed with Sapiens women, Sapiens men could not with Neandertal women). To me all this is simply stunning; thanks to mapping the genomes, we can learn exponentially more than we might from the remains alone.

      1. 3 percent is a lot, especially given the time frames. I do wonder though, could it be that 3% is what is left after those genes have been /diluted/ for millenia? From a genetic point of view, two kinds of genes get passed on from generation to generation – those that are recessives [whether useful or harmful] or those that are /useful/ and possibly dominant. Harmful dominant genes tend to get their carriers killed before they can reproduce.
        But the mere fact that Sapiens, Neanderthals and Denisovans were capable of interbreeding is mind boggling in itself. I’m sure I’ve read somewhere that members of a species have to be pretty ‘close’ to give rise to viable offspring – think horses & donkeys. They can breed but the offspring can’t.
        This is unbelievably exciting.

        1. Yes, there wasn’t too much to choose between the species. We don’t know about the rest of the humans of the day. One of the arguments in the field just now is between ‘lumpers’ and ‘splitters’ – there’s been a suggestion that maybe we’re all just variants of the H. erectus type, which happened to be quite variable. In a sense the whole argument – including division into species – is an illusion of methodology and our tendency to want to divide information up into neat patterns. But at the same time I’ve seen arguments that the inter-species fertility between Neanderthals and Sapiens, particularly, was less than perfect and it’s possible that male offspring were sterile, even if female were not. That, by definition, makes Neanderthals a separate (if close) species.

          1. Good point. Needing to put knowledge into neat little boxes does seem to be a very human trait.
            The whole question is incredibly exciting though. I mean, even if the cross breeding was iffy, the mere fact that they could at all is amazing. I mean, chimps can’t mate with gorillas or orangutans, yet 3 types of homo erectus could mate/breed. Very close indeed.

  4. So interesting! This stuff stirs up all sorts of thoughts. It’s tempting to predict our extinction as a fate we deserve for being too clever, short-sighted, and aggressive for our own (and everything else’s) good. Part of me still thinks Homo sapiens (possibly H. destructor) came from another planet. 🤪

    1. I think we are very much on a course for self-destruction! Where else can we go, as we fight each other to the death while destroying the environment? I suspect it’s a survival system gone wrong; something that worked pretty well back in hunter-gatherer days when populations were very low and survival by any method essential. And every time an environment was destroyed – well, hunter-gatherer groups didn’t have a huge range, so there was always another environment over the next hill. Now… um…yeah. Meanwhile, the fighting has been transmuted into intellectual debate these days, as often as not, but it’s the same sort of thing. There’s a whole branch of the field built around ‘evolutionary psychology’ which I am just dipping into now.

  5. It remains that the other human species have disappeared, though leaving genetic traces behind, as have other ape species. The question too remains: what was the cause, or what were the causes, of their disappearances?

    1. That’s the question – particularly, whether we shared that cause… and got lucky? Or was there something different about us, alone, despite growing evidence that all human species pretty much shared a raft of common characteristics. I’d lean to the former, for now, but there’s always the potential for new evidence.

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