Language and Neanderthal very important 1-2

Neanderthals had a wide range from Europe to the Altai mountains. The oldest potential Neanderthal bones are dated to 430 kya (1) that appear primitive. Later forms are known from numerous fossils, from 130K ya onwards (2). Most of them lived in small groups and about 80% died before the age of 40 (3). Neanderthals interbred with hominins and with "modern humans" (4) but vanished about 30K ya. Only 1–4% of the modern Eurasian genome is derived from Neanderthals (5) and about 20% of the Neanderthal genome survives in modern populations (6).

It is thought that they were "killed off by competition or extermination by migrating humans, climate fluctuations, disease or some combination (7) but the answers may lie in the gene pool. They had a low population, leading to the accumulation of harmful mutations and deformities through inbreeding (1) on account of scattered small groups, short lives, miscarriages and some pertinent factor that also worked to shrink their viable gene pool. Did they split from humans?

There are some obvious differences between humans and Neanderthals. The latter had a more robust and stockier build than humans (8) and adapted to sprinting as opposed to the endurance-oriented, was capable of sudden sprint due to higher proportion of fast-twitch muscle fibers (9) for sudden sprint-hunting.

The Neanderthal braincase averages close or within the range of modern humans (10) but both Neanderthal and human infants measure about 400 cm3 (11). More brain tissue was devoted to bodily maintenance and control, and, for their unique hunting. Consequently, the cognitive areas of the brain were proportionally smaller than in humans (12) including language, attention, social abilities and thought for planning, for

decision making, language comprehension and associations with emotions (13) which would be fairly consistent with the lack or suppressed ability for vocal learning and the absence of speech development as observed by the flat structure at the base of the skull, quite similar to gorilla and chimps. Instead, they had observational learning and apprenticeship skills but lacked innovation (14). Hence, survival of Neanderthals until 30K ya may be entirely due to inbreeding and observational learning.

Exploring ancestry and phylogeny in a complex maze is difficult but must be done for testing. It is conjectured that the Ramapithicine speciation around 6 million years ago gave rise to two types of Australopithicines: one had more orang utan DNA with vocal learning, the other, (probably further south had milder climate fluctuation impact for speciation) and had more chimp genome with observational learning. Varieties of H. erectus interbred with both varieties of Australopithicines (19) giving two lines to the gene pool. One line had vocal learning-enameled teeth with FOXP2. The other had no enamel but was equipped with observational learning. H. erectus interbred with the Orrorins and A. ramidus to give rise to enameled hominins (EH) with speech and with others to yield the non-enameled hominins (NEH) without speech, the ancestors of Neanderthals. Neanderthals, then interbred with EH to yield Denisovans and H. heidelbergensis. The interbreeding went on in Africa and after migrating out of Africa.

After 400,000 years ago and the second interglacial period, unlike the speciation 6 million ya, was different and mild and caused the trend in intra-cranial volume expansion, not via microcephalin in the Neanderthals, who interbred with the EH with FOXP2 but the (fetal and post-birth) gene expression was different and they had no vocal learning. Interbreeding was possible due to similar appearances, as within a clade, but difference in speech capacities became more pronounced over 300K years to set the Neanderthals apart and lost out as observational learning was insufficient, while it forced them to inbreeding, leaving a small percentage of their genes in modern humans through earlier interbreeding, before 40K years. Speech capacity gives vocal learning for sophisticated culture and technology developments that began to accelerate in modern humans.

References

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19. See, Hammer M, article in The Atlantic, by Adam CE, Sep 6, 2011, https://www.theatlantic.com/technology/archive/2011/09/it-wasnt-just-neanderthals-ancient-humans-had-sex-other-hominids/338117/