From Newsgroup: talk.origins

https://www.science.org/content/article/inbreeding-didn-t-doom-neanderthals-study-suggests

https://www.nature.com/articles/s41586-026-10625-1

The Nature paper is open access. The claim is that the researchers have
added 20 Neanderthal genomes to the data set (27 total).

The paper claims that they do not find evidence of a lot of inbreeding
among the Western European Neanderthals. They did not have long
chromosomal stretches of homozygosity (runs of homozygosity) that are
the signs of inbreeding between close relatives. The Neanderthals that
have been identified in the East have shown signs of matings between
close relatives. They think that this was due to the more severe
climate and living conditions that forced the existence of small bands
of survivors. They think that larger populations existed in the West
and inbreeding between close relatives was decreased. The Goyet genomes
from Belgium that were victims of cannibalism and were described as a
possible racial variant of Neanderthals are included in the western
dataset. These individuals were described as gracile and of short
stature compared to the usual Neanderthals, but they definitely had Neanderthal genomes. Their cannibalized remains were found in Belgium,
but isotopes in their bones indicate that they came from somewhere else
in Europe.

The paper does note that the new genomes do contain less genetic
variation than is found among modern human individuals, so there had
been inbreeding in the past due to restricted population size
(Neanderthals survived around 5 glacial periods in the last 600,000
years). It doesn't necessarily mean that there was a population crash
at the start of the last glacial period, but all Neanderthal
mitochondrial genomes coelesce to a single mitochondrial "eve" for the Neanderthal fossils that date back to within the last 100,000 years
(since the return of the last ice age). The Neanderthal eve existed
between 69,000 and 82,000 years ago. This would have been a time when
their territory was decreasing and they would have had to readapt to
glacial conditions. By 45,000 years ago there was a surprising amount
of mitochondrial lineage diversity, but all the lineages were closely
related. Neanderthals would have likely greatly expanded their
population size during the last interglacial period when things got
warmer and more ice melted than has yet melted at this time.

Ron Okimoto

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