Editing Human Origins

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'''Summary'''

The best-supported view in 2025 is that Homo sapiens evolved within Africa from a metapopulation that was already geographically and genetically structured. Over hundreds of thousands of years these African lineages exchanged genes, producing the ancestral diversity shared by all living people today [1]. A subset of these Africans expanded into Eurasia roughly 60–70 kya, where additional, limited gene flow occurred with other hominins such as Neanderthals. 

'''Key points from recent research'''

* Deep structure inside Africa.  
A new structured-coalescent model that fits whole-genome data from people on every inhabited continent shows that the ancestors of modern humans were subdivided for at least 1 million years before the most recent common ancestry of today’s populations [1]. Rather than a single “cradle,” the model supports several long-standing, semi-isolated populations linked by intermittent gene flow.

* Out-of-Africa remains robust.  
Even with deep African structure, all non-African genomes still trace back to an expansion out of Africa within the last 100 kya [1]. This agrees with earlier genetic, palaeo-anthropological and archaeological evidence.

* Adaptive fine-tuning after the expansion.  
A 2024 ancient-DNA meta-analysis reports “pervasive directional selection” in traits tied to diet, immunity and climate adaptation after humans left Africa and settled new environments [3]. This indicates that the species’ origin predates (and is conceptually distinct from) later local adaptations.

'''Public discourse and open questions'''

Razib Khan describes the current picture as “complicated,” noting that the simple “single-origin, single-migration” story has been replaced by a model of “many Africas” and multiple pulses of expansion, contraction and introgression [2]. He emphasises that most researchers now see no contradiction between deep population structure inside Africa and the reality that all living humans are part of one species.

Palaeo-environmental studies highlighted in popular coverage of recent fieldwork underscore how climate shifts—such as the greening and drying of Arabian corridors—created windows that allowed small groups to leave Africa repeatedly [4]. Whether earlier forays left genetic traces, or were completely replaced by the later successful expansion, remains under debate.

'''Points of agreement'''

* All living humans share most of their ancestry with African Homo sapiens that existed ≥300 kya [1][2].  
* A later expansion out of Africa populated the rest of the world and contributed the majority of ancestry outside the continent [1].  
* Subsequent gene flow with archaic hominins was real but limited; it does not challenge the African origin of our species [2].

'''Points of contention'''

* How many semi-independent populations made up the ancestral African metapopulation, and where they were located [1][2].  
* Whether earlier “failed” dispersals left any surviving genetic legacy outside Africa [2][4].  
* The exact timing of the speciation process: some place the morphological roots of Homo sapiens >300 kya, while others propose a more recent genetic definition [1][2].

'''Consensus view'''

In sum, Homo sapiens is an African species that emerged from a long-lived, structured set of populations inside the continent. The single most successful out-of-Africa expansion about 60–70 kya spread those African genomes worldwide, after which local adaptations and limited archaic introgression shaped present-day diversity [1][3].

== Sources ==
# [https://www.nature.com/articles/s41588-025-02117-1 A structured coalescent model reveals deep ancestral structure shared by all modern humans – ''Nature Genetics''] (2025 peer-reviewed research article)
# [https://www.razibkhan.com/p/current-status-its-complicated Current Status: It’s Complicated – ''Razib Khan’s Unsupervised Learning''] (2023 newsletter essay / Blog commentary)
# [https://www.biorxiv.org/content/10.1101/2024.09.14.613021v1 Pervasive findings of directional selection realize the promise of ancient DNA to elucidate human adaptation – ''bioRxiv''] (2024 pre-print; Empirical research)
# https://phys.org/news/2023-10-path-early-human-migrations-once-lush.html

== Question ==
What is the origin of the human species?