Neanderthals in the News

[Recusant]

Maybe the Neanderthals were absorbed by our species rather than simply going extinct. On the other hand an earlier post in this thread describes a steep decline in population of both Neanderthal and anatomically modern humans in the Neanderthal's range. The paper below appears to land on the "same species" side of the discussion. 

"Neanderthals May Never Have Truly Gone Extinct, Study Reveals" | Science Alert

Neanderthals may have never truly gone extinct, according to new research – at least not in the genetic sense.

A new mathematical model has explored a fascinating scenario in which Neanderthals gradually disappeared not through "true extinction" but through genetic absorption into a more prolific species:

Us.

According to the analysis, the long and drawn-out 'love affair' between Homo sapiens and Neanderthals could have led to almost complete genetic absorption within 10,000–30,000 years.

[. . .]

Like all models, this new one is based on imperfect assumptions. It uses the birth rates of modern hunter-gatherer tribes to predict how quickly small Neanderthal tribes would be engulfed by a much larger human population, given how frequently it seems we were interbreeding.

The results are consistent with recent archaeological discoveries and align with a body of evidence that suggests the decline of Neanderthals in Europe was gradual rather than sudden.

Homo sapiens seem to have started migrating out of Africa much earlier than scientists previously thought, and they arrived in Europe in several influxes, possibly starting more than 200,000 years ago.

As each wave of migration came crashing into the region, it engulfed local Neanderthal communities, diluting their genes, like sand pulled into the sea.

[Continues . . .]

The paper is open access:

"A simple analytical model for Neanderthal disappearance due to genetic dilution by recurrent small-scale immigrations of modern humans" | Nature Scientific Reports

Abstract:

The disappearance of Neanderthals remains a subject of intense debate, with competing hypotheses attributing their demise to demographic decline, environmental change, competition with Homo sapiens, or genetic assimilation.

Here, we present a mathematical model demonstrating that small-scale Homo sapiens immigrations into Neanderthal populations, providing recurrent gene mixing, could have led to almost complete genetic substitution over 10,000–30,000 years. Our model, grounded in neutral species drift, does not require selective advantage or catastrophic events but shows that sustained gene flow from a demographically larger species could account for Neanderthals' genetic absorption into modern humans within a time-frame consistent with archaeological evidence.

This scenario aligns with growing evidence of interbreeding and genetic introgression through recurrent H. sapiens immigration waves, providing a parsimonious explanation for the observed patterns of Neanderthal ancestry in present-day Eurasian populations. Although other factors may have contributed to the decline of Neanderthals, our results highlight genetic admixture as a possible key mechanism driving their disappearance.

[Recusant]

If evidence accumulates supporting this ^^^ hypothesis, the "different species" position that I currently favor will be on the ash heap. They can't be a different species if our species basically swallowed them, genetically. 

[Dark Lightning]

I read the original article over there. Kind of a shame to simply be assimilated, but I'd have to say that they migrated from the original, evolved a bit and then got bred back in.

[Recusant]

Yeah, love conquers all, given a broad definition of "love." 

If true, perhaps the same fate befell the Denisovans, given their genetic presence in the modern human genome. I believe I recall that there's genetic evidence of yet a third population that doesn't have a proper name yet.

[Dark Lightning]

Homo Sap. = Borg?

Resistance is futile. You will be assimilated.

 

[Recusant]

It probably was inevitable once we (anatomically modern humans) had developed in Africa. While the Neanderthal evolved to thrive in their territories, in comparison we're adaptable generalists. We just kept coming--the paper talks about the idea of multiple waves of AMH coming out of Africa over a very long time.

[zorkan]

How did Neanderthals start a love affair with humans?
Maybe with a simple peck on the cheek.

https://www.theguardian.com/science/2025/nov/19/neanderthals-early-humans-kissed-research-evolution

[Recusant]

Cool. The paper is open access:

"A comparative approach to the evolution of kissing" | Evolution and Human Behavior

However it happened we shared a particular part of our oral microbiome with Neanderthals.

While modern humans and Neanderthals diverged sometime between 450 and 750 ka, the oral microbe we share (Methanobrevibacter oralis) only separated into distinct strains between 112 and 143 ka (Weyrich et al., 2017). This suggests that commensal microbial species were transferred between modern humans and Neanderthals for some time after the two species split.

[Recusant]

A hypothesis about the disappearance of Neanderthal. Considering that as a species they were around for a relatively long time and were apparently successful, if not as ridiculously dominant as Homo sapiens, the question is: Did something change to bring about this problem?

"Pregnancy complications may have helped wipe out Neanderthals" | Phys.org

Neanderthals disappeared from the fossil record approximately 40,000 years ago. Their extinction was a gradual process over thousands of years, and theories as to why include competition with modern humans and rapid climate change. However, there may have been other contributory factors: preeclampsia and eclampsia.

A new study published in the Journal of Reproductive Immunology suggests that these potentially life-threatening pregnancy complications may have been more severe in our extinct cousins.

Human fetuses are exceptionally energy-demanding owing to their large brains. To meet this demand, the placenta needs to embed deeply into the mother's uterine wall so that blood can flow freely to the fetus. However, if it does not invade deeply enough or remodel the mother's arteries, blood flow is reduced. It then sheds microscopic debris into the mother's blood, signaling that it is under stress.

The mother's body may react by raising its blood pressure, leading to preeclampsia or even eclampsia—the most severe, human‑specific complications of pregnancy. However, this does not always happen. In many cases, when the placenta fails to invade deeply, the mother does not develop preeclampsia. Clinical data suggest that roughly three quarters of fetuses with vascular, growth‑restricted placentas are carried by women who do not show preeclampsia, indicating a significant protective effect. For reasons not yet fully understood, the body sometimes dampens or ignores the placenta's stress signals, which helps protect the mother from dangerous high blood pressure. The baby may be born small as a result, but the mother stays healthy.

In this new study, an international team of physicians and researchers proposes that Neanderthal women lacked this protective mechanism. Consequently, struggling pregnancies may have triggered life-threatening high blood pressure or seizures, significantly reducing reproductive success.

The scientists based this idea on a comparison between modern medical records and ancient Neanderthal DNA. They identified genetic differences that may have affected how pregnancy-related blood pressure is regulated.

[Continues . . .]

The paper is behind a paywall.

Abstract:

Preeclampsia and eclampsia, unique to human reproduction, represent the first disease documented in written history over 5000 years ago, yet their etiology remains elusive in 2026. These disorders, exclusive to Homo sapiens among 4300 mammal species, may have posed an even greater reproductive challenge to Neanderthals, potentially contributing to their poor fecundity.

Arising from incomplete deep trophoblast invasion into maternal spiral arteries, essential for nourishing the energy-demanding fetal brain, they lead to placental insufficiency and fetal growth restriction (FGR). In humans, eclampsia (grand mal seizures) occurs naturally in ∼1 % of pregnancies, while preeclampsia affects 2–8 %, with untreated cases carrying high maternal and fetal mortality.

Predominantly affecting primiparas [first pregnancy] and multiparas with a new partner ("primipaternity"), early-onset preeclampsia (EOP; delivery <34 weeks) results from failed maternal immune tolerance to paternal antigens, causing partial fetal rejection and inadequate artery remodeling. This manifests as FGR with or without maternal syndrome.

Critically, humans evolved a protective mechanism decoupling maternal preeclampsia from ∼75 % of placental FGR cases, averting life-threatening complications. Without this safeguard, preeclampsia rates could soar to 10–20 %, with eclampsia at 4–5 %, severely impeding reproductive success.

Neanderthals, sharing deep hemochorial placentation but possibly lacking this adaptation due to genetic divergences (e.g., imprinted genes, KIR-HLA interactions, PIEZO1 variants), likely suffered higher incidences, exacerbating demographic vulnerabilities like small populations and inbreeding. This hypothesis bridges a gap in paleoanthropology: preeclampsia, the principal human reproductive complication, is never cited by anthropologists as possible explanation of the well-known low fecundity rates in Neanderthals communities.