Reconstructing birth in Australopithecus sediba
Natalie Laudicina, Frankee Rodriguez & Jeremy DeSilva 2019
PLoS https://doi.org/10.1371/journal.pone.0221871

Hominin birth mechanics have been examined & debated from limited & often fragmentary fossil pelvic material:
-some have proposed that birth in the early hominin genus Australopithecus was rel.easy & ape-like,
-others have argued for a more complex, human-like birth mechanism in australopiths,
-still others have hypothesized a unique birth mechanism, with no known modern equivalent.
Preliminary work on the pelvis of the recently discovered 1.98-Ma hominin Au.sediba found it to possess a unique combination of Homo & Australopithecus-like features.

Here, we create a composite pelvis of Au.sediba to reconstruct the birth process in this early hominin.
Consistent with other hominin spp incl.modern humans, the fetus would enter the pelvic inlet in a transverse direction,
but unlike modern humans, the fetus would not need additional rotations to traverse the birth canal.
Further fetal rotation is unnecessary, even with a Homo-like pelvic mid-plane expansion, not seen in earlier hominin spp.
With a birth-canal shape more closely associated with specimens from the genus Homo, and a lack of cephalo-pelvic or shoulder constraints, we therefore find evidence to support the hypothesis that the pelvic morphology of Au.sediba is a result of
locomotor, rather than strictly obstetric constraints.

______

Comment:

Thanks for this interesting article. I fully agree with the conclusion that the australopith pelvis mostly resulted from their locomotion (the newborn's brain size was no problem), but this locomotion was perhaps not what the authors had in mind. Most
likely, early hominoids were already vertical, not for running over open plains as traditionally assumed, but rather for climbing vertically and wading bipedally in the forest swamps where Mio-Pliocene hominoids including australopiths typically
fossilized. The reconstructed Au. sediba pelvis was not that of an early "hominin" (read: human ancestor, to the exclusion Pan & Gorilla), but simply that of an early hominid (sensu: fossil relative of Pan, Homo and Gorilla). The iliac elongation of the
great apes probably evolved during the Pleistocene in parallel in Pongo, Pan and Gorilla, but it did not evolve in Homo, and only to a very limited degree in hylobatids (see e.g. Schultz "The Life of Primates"). For a more thorough discussion, please
google e.g. "Ape and Human evolution 2018 Verhaegen", or see our paper Verhaegen, Puech & Munro 2002 "Aquarboreal Ancestors?" Trends in Ecol. Evol.17:212-7.

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)