Morphological affinities of Homo naledi with other Plio-Pleistocene hominins: a phenetic approach

ABSTRACT Recent fossil material found in Dinaledi Chamber, South Africa, was initially described as a new species of genus Homo, namely Homo naledi. The original study of this new material has pointed to a close proximity with Homo erectus. More recent investigations have, to some extent, confirmed this assignment. Here we present a phenetic analysis based on dentocranial metric variables through Principal Components Analysis and Cluster Analysis based on these fossils and other Plio-Pleistocene hominins. Our results concur that the Dinaledi fossil hominins pertain to genus Homo. However, in our case, their nearest neighbors are Homo habilis and Australopithecus sediba. We suggest that Homo naledi is in fact a South African version of Homo habilis, and not a new species. This can also be applied to Australopithecus sediba.

Periodic Explosive Expansion of Human Retroelements Associated with the Evolution of the Hominoid Primate

Five retroelement families, L1 and L2 (long interspersed nuclear element, LINE), Alu and MIR (short interspersed nuclear element, SINE), and LTR (long terminal repeat), comprise almost half of the human genome. This genome-wide analysis on the time-scaled expansion of retroelements sheds light on the chronologically synchronous amplification peaks of each retroelement family in variable heights across human chromosomes. Especially, L1s and LTRs in the highest density on sex chromosomes Xq and Y, respectively, disclose peak activities that are obscured in autosomes. The periods of young L1, Alu, LTR, and old L1 peak activities calibrated based on sequence divergence coincide with the divergence of the three major hominoid divergence as well as early eutherian radiation while the amplification peaks of old MIR and L2 account for the marsupial-placental split. Overall, the peaks of autonomous LINE (young and old L1s and L2s) peaks and non-autonomous SINE (Alus and MIRs) have alternated repeatedly for 150 million years. In addition, a single burst of LTR parallels the Cretaceous-Tertiary (K-T) boundary, an exceptional global event. These findings suggest that the periodic explosive expansions of LINEs and SINEs and an exceptional burst of LTR comprise the genome dynamics underlying the macroevolution of the hominoid primate lineage.

Evolution and the origins of man: clues from complete sequences of hominoid mitochondrial DNA.

Dating the origins of Homo sapiens sapiens is a central problem in human population genetics and anthropology. Do we descend from a single recent ancestral population in Africa, or from multiple ancestral populations in various regions of the world which one million years ago simultaneously began developing into H.s.sapiens? The high substitution rate of mitochondrial DNA (mtDNA) makes this molecule suitable for genealogical and chronological research on closely related hominoid species. We have analyzed the complete mtDNA sequences of three humans (African, European and Japanese) and two African apes (common chimpanzee and gorilla) in an attempt to estimate more accurately the substitution rates and divergence times of hominoid mtDNAs. Nonsynonymous substitutions and substitutions in RNA genes have accumulated at an approximately constant rate. Under the assumption, supported by the fossil record, that the orangutan and African apes diverged 13 million years ago, we have previously obtained 4.7 million years as the divergence time between humans and chimpanzees. Using this date, we calibrated the substitution rates at synonymous sites and in the displacement-loop region as 4.03 and 7.25 x 10(-8)/site/year, respectively. Based on these rates together with the observation that the African sequence presented here is most diverged from all other human sequences, we inferred the age of the last common ancestor of the human mtDNAs as 140,000 +/- 18,000 years. The result strongly supports the recent African origin of modern humans, H.s. sapiens.