<link rel="stylesheet" href="//fonts.googleapis.com/css?family=Roboto%3A300%2C400%2C500%2C700%7CRoboto+Slab%3A400%2C700">Rare growth defects were common in the stone age - Filthy Monkey Men

In the 1950s, archaeologists found a Neanderthal in Shanidar Cave, Iraq. This ancient bloke had a rough life, suffering from all sorts of injuries; including a missing arm1! He also had growth defects, including a sacral hiatus higher up their tailbone2.

Given all the other things wrong with him, a weird tailbone might seem unimportant. And on its own, it would be. However, another Neanderthal from Shanidar has a similar defect, along with a few other stone age remains from elsewhere. Yet in modern times only <5% have this trait2.

In other words, this defect is more common in stone age fossils than the present day. And it isn’t the only one. A recent survey by Erik Trinakus found dozens of stone age humans and Neanderthals with defects present in a tiny percent of modern people2

The frequency of developmental defects in modern populations versus the number of stone age fossils found with them

What’s going on? Was more going wrong in ancient people? Or maybe, they just buried these people more often, preserving their remains for us to find. 

Lets wildly speculate. 

Defects in the stone age

Fortunately, there are a few steps we can take to reduce the wildness of that speculation. Steps like simply taking a look at these people. For instance, if most of them died young, even if the defect wasn’t that severe, it would be a sure sign they were under severe stress; explaining both the condition and the early death. 

However, if you were hoping it would be that easy I have some bad news for you. Trinkaus was also looking into this possibility and found the evidence didn’t line up. Whilst the people with growth defects were suffering from more stress than you or I – indicated by problems in how their teeth grew – it was actually no worse than in modern hunter-gatherer populations2

On the plus side, this also means these stone age people also didn’t die earlier than normal; possibly thanks to extra medical care from their tribe. So that’s nice2

Instead, maybe injuries were more common back then. A broken bone when young could have knock-on effects during development, particularly if it isn’t set properly. But again, the evidence just doesn’t add up. Whilst some of these growth defects appear to be post-traumatic, the vast majority are not2

(d) features a missing bit of bone that could be the result of trauma, but the rest are more likely to be developmental defects, like extra teeth (I)2

Priority burial

With many explanations for for the increased frequency of growth defects refuted, there is one idea that might still hold water.

See, when we talk about stuff from the stone age, we have to remember we’re only looking at stuff that survived. We don’t have the oldest example of a fossil, we’ve got the oldest example we’ve found. Often, a strange trend might just be a side-effect of this. 

So, it might be the case that something happened to ensure that the people with growth defects survived until the present. Something as simple as being buried in a cave (where there’s protection from the elements) versus an open field (where later construction might cause damage) could bias what we find.  

There is some evidence for this. Burials become more common as the stone age progresses. The number of fossils with growth defects also rises, suggesting burial practices do play an important role in the preservation of these unusual remains2. 

Estimates of remains with growth defects over time. Time goes from left to right

This indicates that there might be a cultural reason we have so many remains with developmental defects. Maybe their tribe were more likely to bury people with these problems, raising the chance they were preserved. Or they buried them in a special location that accidentally enhanced their rate of preservation.

And these are possibilities I find far more fascinating than “they were stressed out”.  

References

  1. Trinkaus, E. and Zimmerman, M.R., 1982. Trauma among the Shanidar Neandertals. American Journal of Physical Anthropology57(1), pp.61-76.
  2. Trinkaus, E., 2018. An abundance of developmental anomalies and abnormalities in Pleistocene people. Proceedings of the National Academy of Sciences115(47), pp.11941-11946.

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2 Comments

Andy Milroy · 21st December 2018 at 9:41 am

Adam,

Remember that the Neanderthals were living in small isolated groups, prone to inbreeding which can case genetic defects or amplify them..

Best wishes

Andy

    Adam Benton · 23rd December 2018 at 10:19 am

    There is some potential there, and the repetition of some traits at the same site suggests there may be a familial cause. However, modern humans were also plagued with these issues; suggesting inbreeding cannot be the sole cause for all this.

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