Hominin evolution was caused by introgression from Gorilla
- Published
- Accepted
- Subject Areas
- Anthropology, Evolutionary Studies, Genomics, Paleontology
- Keywords
- ps5, australopithecus, paranthropus, introgression, evolution, phylogenetics, hybridization, gorilla, pan, homo
- Copyright
- © 2018 Nygren
- Licence
- This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, reproduction and adaptation in any medium and for any purpose provided that it is properly attributed. For attribution, the original author(s), title, publication source (PeerJ Preprints) and either DOI or URL of the article must be cited.
- Cite this article
- 2018. Hominin evolution was caused by introgression from Gorilla. PeerJ Preprints 6:e27163v1 https://doi.org/10.7287/peerj.preprints.27163v1
Abstract
ABSTRACT: The discovery of Paranthropus deyiremeda in 3.3–3.5 million year old fossil sites in Afar, together with 30% of the gorilla genome showing lineage sorting between humans and chimpanzees, and a NUMT (“nuclear mitochondrial DNA segment”) on chromosome 5 that is shared by both gorillas, humans and chimpanzees, and shown to have diverged at the time of the Pan-Homo split rather than the Gorilla/Pan-Homo split, provides conclusive evidence that introgression from the gorilla lineage caused the Pan-Homo split, and the speciation of both the Australopithecus lineage and the Paranthropus lineage.
Author Comment
The manuscript is a third iteration of an ideation, where each version takes a slightly different perspective, to cover a similar research topic. The first version was organized around Pliocene hominins and the speciation of Paranthropus and Australopithecus, the second turned the attention to where most people focus their attention, the Human-Chimpanzee split. This third iteration integrates the perspective of the two previous ones, and looks at Hominin evolution overall, both the Pan-Homo split and the speciation of Australopithecus and Paranthropus, and includes new content, a visualization of the ps5 NUMT tree based on the revised estimate for the time of the insertion of ps5.
Supplemental Information
Figure 1: Phylogenetic tree showing how Gorilla introgression caused the human-chimpanzee split
Phylogenetic tree showing how introgression caused the speciation of humans. This introgression speciation model predicts an early split for Paranthropus and Australopithecus, increasingly shown in the fossil record (Haile-Selassie, 2015, 2016; Wood, 2016), and also shows that the evolution of genes that ended up in Australopithecus, and therefore in extant humans, as well as in Paranthropus, can and should be traced along the gorilla lineage as well
Figure 2. Morphological traits in Gorilla and the hybrid lineages Paranthropus and Australopithecus
Introgression from Gorilla caused the speciation of both Australopithecus and Paranthropus, and means that traits that have evolved independently in the gorilla lineage were transferred into the hybrid lineages. Paranthropus are often described as “gorilla-like”, they have sagittal crests which suggest strong muscles of mastication, and broad, grinding herbivorous teeth, that led to the name “nutcracker man” for Paranthropus boisei who lived between 2.4–1.4 Ma.
Figure 2. Morphological traits in Gorilla and the hybrid lineages Paranthropus and Australopithecus
Introgression from Gorilla caused the speciation of both Australopithecus and Paranthropus, and means that traits that have evolved independently in the gorilla lineage were transferred into the hybrid lineages. Paranthropus are often described as “gorilla-like”, they have sagittal crests which suggest strong muscles of mastication, and broad, grinding herbivorous teeth, that led to the name “nutcracker man” for Paranthropus boisei who lived between 2.4–1.4 Ma.
Figure 2. Morphological traits in Gorilla and the hybrid lineages Paranthropus and Australopithecus
Introgression from Gorilla caused the speciation of both Australopithecus and Paranthropus, and means that traits that have evolved independently in the gorilla lineage were transferred into the hybrid lineages. Paranthropus are often described as “gorilla-like”, they have sagittal crests which suggest strong muscles of mastication, and broad, grinding herbivorous teeth, that led to the name “nutcracker man” for Paranthropus boisei who lived between 2.4–1.4 Ma.
Fig. 3. Phylogenetic tree with hominine mtDNA and ps5 homologs
Joint phylogenetic tree of hominine mtDNA and the ps5 pseudogene of mtDNA. Black and pink lines depict the mitochondrial and the pseudogene lineages respectively, diverging from their mitochondrial common ancestor. The insertion of mtDNA fragments into the nuclear genome of Gorilla can be roughly estimated to 1.8 Myr after the Gorilla/Pan-Homo split, and the transfer to Pan and Homo to the human-chimpanzee split, along with 30% of the Gorilla genome.
Fig. 4. Fossil record for a taxonomic classification of Paranthropus deyiremeda
The Burtele foot, BRT-VP-2/73, found in 2009 (Haile-Selassie, 2015) in Burtele at Woranso-Mille, Afar, tentatively assigned Au. deyiremeda (Haile-Selassie, 2015), contemporaneous with Au. afarensis, shows distinct locomotor adaptation as it retains a grasping hallux, in contrast to the human-like adducted hallux that had developed in Australopithecus afarensis. The conclusive evidence that hominin evolution was caused by introgression from Gorilla suggests that Au. deyiremeda is better classified as Paranthropus deyiremeda. With a revised taxonomic classification, building on a combination of genomic data and fossil records, it can be predicted that Paranthropus and Australopithecus, like Pan and Homo, diverged through lineage sorting as the two lineages co-opted genes from the Gorilla lineage to adapt for separate niches.
Fig. 5. Gorilla-like traits in the Paranthropus lineage a result of lineage sorting from Gorilla
Paranthropus aethiopicus, 2.8-2.3 Ma, with gorilla-like sagittal cranial crests as an attachment for strong muscles of mastication, a dietary adaptation. The genetic proof of an introgression event at the time of the Pan-Homo spit shows that the most parsimonious origin for those features within Paranthropus was lineage sorting from the introgression event, originating in Gorilla, rather than convergent evolution. Image from the public domain (CC BY-SA 3.0).
