New Chinese hominin species #2: Is it a new species?

ResearchBlogging.org<- Part 1 came before

As many of you are likely aware by this point, some interesting remains have recently been discovered in China. These have been purported to contain a novel mixture of modern, ancient and never seen before traits, around which two major hypotheses have been discovered.

  1. These are examples of an archaic group of hominins that survived until modern times, going on their own evolutionary journey during that time
  2. These are examples of an early human migration into China that, for one reason or another, retained archaic traits (which also undertook their own evolutionary journey)

If either of these ideas were correct it would require a fascinating change to the story of human evolution but of course, for any of these hypotheses to be correct would require that the researchers claims are true. Namely, that these specimens are from the dates they say they are and contain the strange features the researchers say they do.

Having discussed the dating in part 1 of this series, this post moves onto their peculiar anatomy!

Preliminary conclusions: odd looking

But first, a quick warning. A proper anatomical and statistical analysis requires more resources than an undergraduate writing a part-time blog has access to and so what I am about to say is far from the final word on the subject.

Caveats aside, lets continue!

Anatomy

The paper lists a few features their specimens have in common with humans and those which are believed to be archaic/novel. This is based of a comparison with a variety of other Homo specimens, including humans from a range of time periods, neanderthals and Homo erectus.

This comparison seems fairly extensive with a relatively large sample size, taking finds from around the world as well as from different time periods. My one qualm with it is that very few of the specimens this individual is being compared against date from the same time period.

Whilst I wouldn’t expect this to fundamentally alter the results, given we know humans can change quite a bit and so it is not impossible that a more temporally relevant comparison would remove some of the weaker effects (i.e. where there is only a few millimetres difference).

But are there even any effects?

You're probably going to need this

The short answer is yes. Several of the differences postulated by the paper do exist, including (but not limited to)

  • The parietal bones are smaller, as are the reconstructed parietal lobes (so called because they sit under the parietal bone) of the brain
  • The mandible is smaller but broader, with many of its features either differently placed or completely absent. The maxilla is also broader
  • The zygomatic arch (cheek bone) is significantly larger, more angled and flared when compared to humans
  • Smaller nasal bones
  • The rear teeth are broader, despite having smaller roots

However, most of the measurements involved are only slightly different to anatomically modern humans and seem to fall nicely into the range of older human specimens. Indeed, other than the small nasal bones there seems to be no measurement which is not present in any other Homo specimen.

  • The parietal bones, whilst smaller, are still within the margin of error for modern humans and fit comfortably in the range of neanderthals.
  • Some aspects of the mandible are similar to early Eurasian humans, whilst other features not common to them are present in archaic Homo.
  • The zygomatic arch is similar to early African humans and neanderthals
  • The nasal bones are just bizarre
  • The rear teeth fall within the range of most members of Homo although are closest to neanderthals.

What I just said in graph form. Kind of.

So the oddness of these specimens isn’t so much that they include brand new traits, it’s just they have an odd mixture of existing ones. The thing is, such mixtures aren’t unheard of in the fossil record.

When Homo sapiens first emerged from its ancestors, “archaic Homo sapiens,” many of these individuals had a peculiar mixture of traits. Our early history was one of several different populations, each of which had a slightly different combination of traits. These different combinations aren’t each viewed as individual species, as such I don’t believe this new hominin should either.

Further none of these combinations ever really rose to prominence – just look at the variation within humans today. Instead, some of these combinations either changed or disappeared (we underwent a population bottleneck at one point which meant all the survivors probably looked alike) until we were left with a broad group of individuals who all looked kind of the same yet kind of not.

However, these “mixture” humans are all rather old, dating to over 100,000 years prior to the period the Chinese specimen lived. The biggest issue of contention then is not so much what they looked like but when they lived. In part 1 I discussed the dating of these finds and noted that for some of the specimens it is something to be skeptical of, whilst even the best dated find could use some improvement.

This is the first true human and even he looks kinda funny (and not just because the skull is missing bits)

So I believe these specimens to be the early African humans, with their combination of traits, who migrated into China at some point. I would expect that the dates for these individuals to be pushed back, making this scenario even more plausible.

But if it isn’t redated, if the fact it disagrees with my ideas doesn’t mean it’s wrong? Then we have a late surviving archaic population that moved to China at some point. Throughout this history, it somehow managed to remain isolated and thus preserve its combination of traits.

This is harder to believe than if  the Chinese specimens are older, but still very plausible. Many suspect Homo floresiensis (the hobbit) followed a similar path of an early population (albeit one even earlier than archaic humans) migrating and becoming isolated.

Of course, they did wind up on an island which makes isolation easier. The “red deer people” lived quite near to modern humans. However, we might have only found an outlier population – most have them could’ve lived in a more isolated refuge, with these individuals having strolled too near to humans.

Whatever the case, this find remains fascinating and I intend to keep you updated of further developments.

Curnoe D, Xueping J, Herries AI, Kanning B, Taçon PS, Zhende B, Fink D, Yunsheng Z, Hellstrom J, Yun L, Cassis G, Bing S, Wroe S, Shi H, Parr WC, Shengmin H, & Rogers N (2012). Human remains from the pleistocene-holocene transition of southwest china suggest a complex evolutionary history for East asians. PloS one, 7 (3) PMID: 22431968
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2 thoughts on “New Chinese hominin species #2: Is it a new species?

  1. Pingback: Recent changes to the human accelerated region | EvoAnth

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