Australopithecus anamensis 4 million years old?

A new dating technique suggests that a human-like fossil skeleton found in South Africa was buried about 4 million years ago, which makes it one of the oldest known hominid discoveries. That's 1 million years earlier than previously thought.

The nearly complete skeleton came from the Sterkfontein caves that contain rich deposits of remains from the pre-human branches of the ancestral tree that led to modern humans. The bones are identified as a type of Australopithecus, an extinct form of pre-humans.

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Damn, now thats interesting

Deep, you keep finding some very good articles!

I spoke with an anthropology instructor at the university I attended, who had worked with the Leaky's. According to her, there is a good chance that the dating used on other finds could be faulty, and a good likelihood that Australopithicus could be as old as 5 million years.

As pointed out at the end of the article, the main problem with such dating is that we have no certainty that the sediments found concurrently with the skelton were in fact from the same time frame.

Pretty much the only real way to be certain of the date of such fossils is if you have a find where they have been buried in volcanic ash. Since the ash was obviously newly generated at time of deposition, coincident with the fossil, then you can determine overall age through radiometric dating from the ash. In such cases, the ashfall is usually the reason the fossil is found there in the first place.

Very interesting and informative thread!

A good find, indeed: interesting that it's South Africa rather than the East-Central Kenya regions we have become accustomed to.
Information on the "new" technique would be interesting: is it new, or is it a refinement of existing (e.g. carbon-based) techniques?

Information on the "new" technique would be interesting: is it new, or is it a refinement of existing (e.g. carbon-based) techniques? Posted by Estragon

It mentions a radiometric dating technique using unstable isotopes of aluminum and berryllium and Cosmic Rays (this must be new, I have never heard of it). Carbon 14 dating usually only has a an effective range of about 100 years to 75,000 years with a margin for error of between 200-1000 years (error margin increases the further back you go). I have heard something about a new technique for Carbon 14 that they can get up to 150,000 years effective range, but have never tried it, so dont know much about it.

Sedimentary deposits are notoriously difficult to date accurately, because they are not what is called parent deposition. In other words, if you find a fossil buried in sand and gravel, and you date that gravel using a normal radiometric method (say, potassium/argon), the date you get is the date that the original magma crystallized... it could be millions of years from the time this magma crystallized until it weathered, broke down, and formed gravel that found its way into wherever you found it... and it could then be many more years until your fossil find was deposited where you found it.

There are some dating methods where you measure mineral formation on the fossil, or inside voids of the fossil, if such minerals form at a known rate. However, such methods are not any more accurate, and have a limited date range as well.