Australopithecus sediba Dismissed as Human Ancestor
Two paleoanthropologists writing in Science explain why the mysterious A. sediba is unlikely to be related to the genus Homo.
Temporal evidence shows Australopithecus sediba is unlikely to be the ancestor of Homo (Science Magazine). University of Chicago paleoanthropologists Andrew Du and Zeresenay Alemseged explain why they believe this creature, wherever it was on the evolutionary tree (they are evolutionists), does not belong on the branch leading to us.
Understanding the emergence of the genus Homo is a pressing problem in the study of human origins. Australopithecus sediba has recently been proposed as the ancestral species of Homo, although it postdates earliest Homo by 800,000 years. Here, we use probability models to demonstrate that observing an ancestor’s fossil horizon that is at least 800,000 years younger than the descendant’s fossil horizon is unlikely (about 0.09% on average). We corroborate these results by searching the literature and finding that within pairs of purported hominin ancestor–descendant species, in only one case did the first-discovered fossil in the ancestor postdate that from the descendant, and the age difference between these fossils was much less than the difference observed between A. sediba and earliest Homo. Together, these results suggest it is highly unlikely that A. sediba is ancestral to Homo, and the most viable candidate ancestral species remains Australopithecus afarensis.
You can’t be younger than your descendants. That’s illogical, they say. So, it’s back to Lucy. Du and Alemseged have effectively taken a transitional form out of the line, leaving a bigger gap between Lucy (an ape) and the earliest Homo candidate.
Are scientists now closer to understanding how human beings evolved from ape-like beings? Hear what they say in conclusion:
The issue of the origin of Homo is one of the thorniest questions in paleoanthropology and one that has led to myriad proposals and, sometimes, speculations. Answers to the questions of how, when, and where the earliest representatives of the genus emerged are still in flux, owing especially to the dearth of fossil data from the relevant temporal range (3.0 to 2.5 Ma ago). It is therefore important to use all available lines of evidence when addressing a question as data poor as this one. While fossil remains from the 3.0- to 2.5-Ma-old interval are necessary to reasonably document the morphological patterns surrounding the origin of Homo, probabilistic methods such as the one used here are also critical for assessing the chronological evidence for proposed relationships between Homo and candidate ancestors. Hypothesized ancestor-descendant relationships must satisfy both temporal and morphological criteria. We tested the first criterion here, and the second one has been tested elsewhere. A. sediba fails both benchmarks, and the most viable ancestral candidate for the genus Homo remains Australopithecus afarensis both on morphological and temporal grounds.
For earlier articles about A. sediba, which was announced by Lee Berger in 2010, see:
- Another Fossil Human Ancestor Claimed (8 April 2010)
- Media Respond Predictably to Latest Ape-Man (8 September 2011)
- The Blind Men and the Ape Man (25 October 2011)
- Early Man Stories Evolve (11 December 2011)
- Eats Shoots and Leaves (8 July 2012)
- Divorce Spats Between Lucy and Designated Replacement (15 April 2013)
- Genetic Dating Can Fool Scientists (1 June 2013)
Christopher Rupe and John Sanford, in their book Contested Bones, look at the evidence and conclude that A. sediba was not a species at all, but a mixture of bones from different creatures.
Thus Lee Berger’s pet monkey falls off the tree. Farewell, Sediba. Maybe you can get a date with Lucy. Share your lessons about desiring fame as a Homo-wannabee with her.
Notice what these authors said about their field. Dearth of fossil data. Data poor. Thorny. Sediba fails the morphology test. Sediba fails the temporal test. Don’t know how, when, and where the earliest representatives of the genus “emerged.”
That’s been the situation in paleoanthropology since Darwin. Empirically speaking, apes are apes, humans are humans, and never the twain shall meet. The “March of Progress” icon is one of the biggest propaganda hoaxes ever sprung on the public (10 April 2018).