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Tuesday, September 15, 2015

Did ancient hominids bury their dead?

Yesterday, I told you how Homo naledi was discovered. To refresh your memory, check out this picture:

Marina Elliott works in the Rising Star cave near Johannesburg, South Africa. (National Geographic/National Geographic)
Today, we'll discuss why this find was so important.

The very fact that so many bones were found in one place was critical. The six paleontologist spelunkers retrieved over 1500 bone fragments which were later assembled into at least 15 skeletons. That means that the researchers had specimens of different ages and of both genders, an almost unheard of scientific find. This gave anthropologists an unusually accurate picture of what these creatures were like. 

Thus, we know that H. naledi's physical features place it between those found in the genera Australopithecus and Homo.
We don't yet know how old those bones are, which means we can't be sure where H. nelida falls on our family tree. H. nelida seems to be intermediate between Austrolopithecus and Homo, but could have been contemporaneous with most of the species within those genera. Dating the fossils is going to give us critical information on how and when different modern physical traits first appeared. 

Just as importantly, how did those bones find their way into that remote cavity? Consider that although there were so many H. naledi bones in the cave, virtually no other species were found along side them. This was not a lair used by predators, hominid or otherwise, nor was the accumulation of bones due to flooding or other natural causes. There were no marks of damage or scavenging on the bones, so the cave was not the site of a slaughter or feast. And remember that the chamber where the bones were found is extremely hard to access. 

Lead researcher Lee Berger's working hypothesis is that the bodies were deliberately placed in the chamber, most likely by dropping them in from above. We have a name for procedures like this: it's called 'burial', and it's not an activity we would have associated with creatures that had brains the size of gorillas. 

Berger and the other researchers are continuing to study the fossils. Many more interesting conclusions are sure to come out of this amazing find. You can find some great photographs as well as an artist's rendition of the creatures giving a dead relative the old heave-ho in the National Geographic story by Jamie Shreeve. 

Berger, L., Hawks, J., de Ruiter, D., Churchill, S., Schmid, P., Delezene, L., Kivell, T., Garvin, H., Williams, S., DeSilva, J.... (2015) , a new species of the genus from the Dinaledi Chamber, South Africa . eLife. DOI: 10.7554/eLife.09560  

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