Bones reveal first evidence of Down syndrome in Neanderthals

June 27, 2024 9:34 AM

The inner ear bones from this close relative of ours suggest both that they had Down syndrome and that they were cared for by their community.
posted by brundlefly (16 comments total)

died at about age 50 with impaired vision and hearing and one arm partially amputated—conditions he could only have survived with the help of others.

There's a famous (though unproven) quote about this by anthropologist Margaret Mead:

Mead said that the first sign of civilization in an ancient culture was a femur (thighbone) that had been broken and then healed. Mead explained that in the animal kingdom, if you break your leg, you die. You cannot run from danger, get to the river for a drink or hunt for food. You are meat for prowling beasts. No animal survives a broken leg long enough for the bone to heal.

A broken femur that has healed is evidence that someone has taken time to stay with the one who fell, has bound up the wound, has carried the person to safety and has tended the person through recovery. Helping someone else through difficulty is where civilization starts.
posted by AlSweigart at 10:29 AM on June 27 [8 favorites]

No animal survives a broken leg long enough for the bone to heal
Are we sure of this?
posted by 922257033c4a0f3cecdbd819a46d626999d1af4a at 11:04 AM on June 27

If it can get food and get away from predators despite the injury, it will survive, but that’s a tall order for most critters. I imagine Mead was exaggerating rhetorically.
posted by AdamCSnider at 11:24 AM on June 27 [1 favorite]

My business partner lives on a few acres on an island and reports that a goose with a broken leg lived four years as part of a flock that spent midsummer through fall on her land even though it could barely walk the whole time.

She’s also had coyotes with obviously broken legs show up in her birch grove accompanied by a very attentive partner, and then leave within a couple of weeks apparently completely healed.
posted by jamjam at 11:51 AM on June 27 [4 favorites]

The clear conclusion is that geese and wolves are civilized, no?
posted by signal at 12:24 PM on June 27 [11 favorites]

Crows too.
posted by I claim sanctuary at 12:38 PM on June 27 [3 favorites]

Y'all, the point of the Mead quote was probably better illustrated through the preamble that got omitted from the comment: the fact that someone asked Mead about what the earliest artifact we had that she knew of which illustrated Human Civilization. The person had been expecting Mead to say something about a pot or a stone ax or some other kind of tool, because they were no doubt speaking from a perspective of "what makes man important is our ability to make objects". But Mead's response was more about "No, what makes man important is our ability to live in a more or less harmonious society".

The fact that there are some animals who may also exhibit this trait, and there are some other animals who also have societies and may use tools, is a little bit beside the point; it's more about Mead re-framing the narrative that what made mankind special was our compassion as opposed to our strength or our skill.
posted by EmpressCallipygos at 12:50 PM on June 27 [22 favorites]

But isn't that also what makes crows, geese, and wolves special?
posted by signal at 1:09 PM on June 27 [3 favorites]

Please forgive me getting any of this wrong I have a very surface understanding of it all -

So (as I understand it) modern humans are all descendants of Homo sapiens or Neanderthals or a combination of the two.

Does this discovery mean that the genetic mutation that results in people with Downs come from the Neanderthal branch of the ancestoral tree ?
posted by Faintdreams at 1:37 PM on June 27

Faintdreams, Down syndrome happens when an embryo erroneously develops a third copy of Chromosome 21 - it's a mistake during cell division, not a heritable condition.
posted by McBearclaw at 2:15 PM on June 27 [12 favorites]

Ah. Thanks for the reply, I thought Downs was a random (known parameter) gene mutation. My apologies.
posted by Faintdreams at 2:18 PM on June 27

Most animals seem not to get it, but other apes apparently can.
posted by AdamCSnider at 2:18 PM on June 27 [2 favorites]

Faintdreams, there was news about genetic inheritance, Neanderthals, and a modern-day disease (Dupuytren's contracture, aka Viking disease) around this time last year. “Major genetic risk factors for Dupuytren's disease are inherited from Neanderthals,” Molecular Biology and Evolution, Volume 40, Issue 6, June 2023
posted by Iris Gambol at 4:36 PM on June 27 [3 favorites]

Huh I will blame my Dupuytren's disease to vikings instead of booze!!!
posted by supermedusa at 6:33 PM on June 27 [2 favorites]

This is really cool. Makes me feel better about being alive. Thanks, brundlefly!
posted by bunderful at 8:45 PM on June 27 [1 favorite]

Somatic chromosomes are numbered according to their size, with chromosome 1 being the largest, but 21 and 22 are so similar in size that scientists got the numbering wrong and 21 is actually smaller than 22.

This is too much for coincidence in my opinion, and it seems more than merely possible to me that they started out as twins as a result of some kind of duplication event and diverged over evolutionary time, but a plausible scenario is hard to imagine.

The most recent major chromosomal rearrangement in humans is apparently the fusion of two smaller chromosomes into chromosome 2:

Most living people have 23 pairs of chromosomes, as did our relatives known from ancient DNA, the Neandertals and Denisovans. All of our closest primate relatives—chimpanzees, bonobos, gorillas, and orangutans—have 24 pairs. From comparing these genomes with each other, it is clear that sometime during human evolution two ancestral chromosomes fused together, reducing our number. The product of that fusion is human chromosome 2, the second-largest of our chromosomes.

Evolutionary geneticists often focus closely on differences in chromosome numbers, which can be related to reproductive incompatibility between sister species. Structural changes to chromosomes may also affect gene regulation or other functions. Did the chromosome 2 fusion make a difference to our ancestors, maybe even cause an ancient speciation in our lineage?

Maybe the biggest barrier to understanding how this chromosome fusion mattered is a better knowledge of exactly when it happened. Recently geneticists led by Barbara Poszewiecka applied a creative approach to estimate how long ago the two ancestral chromosomes fused together. They found a surprisingly recent range of times: between 400,000 and 1.5 million years ago.

A new paper just published suggests that a major bottleneck in our evolutionary history happened between 930,000 and 800,000 years ago, and points to the chromosome 2 fusion as one possible consequence. This interval is a very interesting time. Our African ancestors, Neandertal ancestors, and Denisovan ancestors all diverged from each other around 700,000 years ago—and all these branches share the fused chromosome. It seems likely that the population that gave rise to these later hominins was the one in which the chromosome 2 fusion first evolved. That may have made a big difference to their interaction with other hominins that lived at the same time.

posted by jamjam at 11:01 PM on June 27 [5 favorites]