This Anthro Life

Dating your Ancestors is Complicated: The Strange Case of Homo Naledi

Photo: John Hawks. Homo naledi has much in common with early forms of the genus Homo

On this episode, Adam and Ryan dive into the complexities of our ever evolving human family. How we understand our ancient ancestors, cousins, and ape family has the potential to impact our understanding of what it means to be human and how we are still changing. The new and exciting data we dive into this episode is all about Homo Naledi, perhaps the most recent addition to our family. As of the day we recorded this episode, April 25th, the first concrete date range for the species was publicized (but stay tuned for further developments). Rather than being very early (that is more ancient) and dating to the time of the earliest Homo Erectus specimens as originally hypothesized (some 2 million years ago), it now appears that Naledi was potentially a contemporary of the earliest Homo Sapiens (that’s us) ranging from 200 to 300 thousand years ago. This means we need to re-evaluate our genus once again and think about the complexities of dating our ancestors.

Quick definitions:

  • Species – a group of living organisms consisting of similar individuals capable of exchanging genes or interbreeding; Homo, Australopicus
  • Genus – one step below species on the taxonomic system: A. afarensis (Lucy), H. sapiens (us), H. neandertal, H. naledi

Links to the story so far:

https://www.sciencenews.org/article/homo-naledis-brain-shows-humanlike-features. – Naledi’s brain is wired much like modern humans, having developed regions that relate to strong emotions including empathy. Granted, this article came out slightly before the new dating was announced and concludes that human emotions likely developed earlier than thought… not the case now, but it is fun to think that our cousins have cool feelings too.

The latest from New Scientist: Homo naledi is only 250,000 years old – here’s why that matters

BBC keeps us thinking: Primitive human ‘lived much more recently – naledi is now thought to date between 300 and 200 kya, surprise! But, the methods for this dating are not yet available…

Questions and Themes of the Episode:

  • An Evolutionary mystery: Between 3 and 2 million years ago Homo sapiens emerged. On the earlier side (3 million years) are Australopithecus afarensis (Lucy), discovered in 1974; On the later side (2 million years) are Homo erectus ( a tool-wielding, fire-making, globe-trotting species with a big brain and body proportions much like ours.) One of the big questions that remains with human origins is how to understand the several likely links between them, and what the evidence might look like. (Thanks Nat Geo)
  • Why is it so difficult to age fossilized skeletons? – 3 ways of dating bones: isotopic analysis, surrounding rock, relative to other fossils in found in the same general stratigraphic area.
  • What features make H. naledi unique: legs and feet for long distance walking (not necessarily running, a hallmark of the genus Homo, particularly H. erectus), curved fingers (evidence of climbing usually observed with more primitive ancestors like the Australopithecus) small jaws and front teeth (modern) more primitive rear dentition; relatively small skull size (like chimpanzees)
    • Skulls: Primitive, similar to Homo habilis. Between 466 and 560 cc, in comparison to H. habilis 510 to 700 cc, H. erectus 550 to 1100 cc, H. floresiensis 426 cc.
    • 1,550 fossils from at least 15 individuals. Full range of ages, from birth to old age. (source)
  • Fluidity of evolution
    • Implications – are there are actually more offshoots than we thought
    • Might we have bred with H. naledi? (Speculate on skeletal and genetic evidence)
    • Did they live at the same time as H. sapiens?
      • Earliest homo appear about 2 million years ago – the “base” of the family tree, but if H. naledi is only 200 Ky, it’s not at the base at all.
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