When a study published in Science in February 2026 showed a striking pattern of Neanderthal DNA depletion on the X chromosome of modern humans, the media response was swift and romantic. Headlines announced that Neanderthal men “chose” or “had designs on” Homo sapiens women. But Ludovic Slimak, a CNRS archaeologist at the Center for Anthropobiology and Genomics of Toulouse, argues the genetic data tells a very different story — one about social structure, mobility rules, and possibly violence, not prehistoric romance.
“The study in question shows nothing of the sort,” Slimak writes in The Conversation. He argues that the Science paper by Platt, Harris, and Tishkoff explicitly tests three hypotheses — natural selection, sex-biased demographics, and partner preference — and concludes that partner preference is “one possible parsimonious mechanism” that “excludes neither demographic bias nor more complex scenarios.”
The genetic asymmetry
The central observation is well-established: in present-day non-African humans, Neanderthal DNA is distributed unevenly across the genome. It is more frequent on the non-sex chromosomes (autosomes) and strongly depleted on the X chromosome. The Science study quantified this asymmetry, finding a 62 percent relative excess of modern human ancestry on Neanderthal X chromosomes compared to Neanderthal autosomes — a mirror-image pattern.
The most common interpretation — that Neanderthal X-linked genes were simply toxic to modern humans — is ruled out by this mirror pattern. If X-linked Neanderthal genes were harmful in modern humans, the reverse would also hold: human DNA would be absent from Neanderthal X chromosomes. But the opposite was observed.
Because females carry two X chromosomes and males carry one, the X chromosome spends two-thirds of its time in females. If most pairings were Neanderthal males with sapiens females, the X chromosomes that crossed species boundaries would be biased toward the female parent. This is the basis for the “mate preference” interpretation.
Patrilocality and unequal exchange
Slimak draws on archaeological evidence from two key Neanderthal sites to build an alternative framework.
At El Sidrón Cave in Asturias, northern Spain, the remains of 12-13 Neanderthals interpreted as a contemporaneous social group revealed a striking genetic pattern. Three adult males all shared the same mitochondrial lineage (inherited through the mother), while three adult females each carried different mitochondrial lineages (Lalueza-Fox et al., PNAS, 2011). This is a classic signature of patrilocality: males stayed in their natal group; females moved between groups. This pattern is common among great apes and approximately 70 percent of known human societies.
At Goyet Cave in Belgium, the remains of four Neanderthal females and two immature individuals showed clear cut-marks, with isotopic signatures indicating non-local geographic origin. The excavators advanced the hypothesis of conflict-related cannibalism targeting females from neighboring groups.
The direction problem
The strongest argument against the romantic narrative is temporal. The Science study refers to a very ancient admixture event approximately 250,000 years ago, then extrapolates the same mechanism across 200,000 years until the final Neanderthal-Sapiens contacts around 50,000-40,000 years ago.
“Among the earliest ancient Sapiens in Eurasia, Neanderthal ancestry is constant,” Slimak writes. “By contrast, the Neanderthal genomes available so far document no recent Sapiens contribution within the last Neanderthal populations.”
If sapiens women were regularly entering Neanderthal groups — as the romantic narrative implies — some sapiens DNA should appear in late Neanderthal genomes. It does not. The gene flow was one-directional: from Neanderthals into sapiens, but not back.
Slimak’s proposed alternative is that the genetic pattern reflects patrilocality combined with unequal group exchange — Neanderthal females may have been incorporated into sapiens groups, but Neanderthal groups did not incorporate sapiens females. This could reflect capture, raiding, asymmetrical alliances, demographic pressure, or social hierarchy between groups.
“Genetics detects transmissions. It does not reconstruct a society,” Slimak concludes. “It tells us neither whether these unions involved alliances, captures, asymmetrical exchanges, violence, or choice.”
Not the only alternative
The Science study’s own authors acknowledge the limits of their interpretation. Alexander Platt, the lead author, told Live Science: “I have no idea whose preference is being expressed here.” The study notes that it “cannot exclude the possibility of demographic sex biases playing an important role” and that “differential migration and mate preference may all have been at play simultaneously.”
Outside experts have urged similar caution. Ignacio Martín Lerma of the University of Murcia, speaking to Science Media Center Spain, noted that “these are demographic inferences based on population models rather than direct evidence of specific behaviors.” Javier Baena of the Autonomous University of Madrid added that “these paleogenetic studies tend to suffer from a lack of integration with archaeological data.”
The Neanderthal romance narrative makes for good headlines. But as Slimak argues, the underlying science — and the 200,000 years of actual human and Neanderthal social life it attempts to explain — is considerably more complex, and considerably less romantic.
Sources
1. ScienceDaily, “The Neanderthal ‘love story’ isn’t what the DNA actually shows” (7 July 2026). https://www.sciencedaily.com/releases/2026/06/260626030443.htm
2. Slimak, L., “A matter of taste: did Neanderthals really like Sapiens women?”, The Conversation (3 April 2026).
3. Platt, A., Harris, K. & Tishkoff, S., “Interbreeding between Neanderthals and modern humans was strongly sex biased”, Science (2026). DOI: 10.1126/science.aea6774
4. Lalueza-Fox, C. et al., “Genetic analysis of a Neanderthal group from El Sidrón”, PNAS (2011).