Prof Lee Berger’s announcement on Tuesday (9 May 2017) that the bones of
Homo naledi have been reliably dated to between 236,000 and 335,000 years old
is big news. It is also big news that his collaborators have found another
chamber within the Rising Star cave system near Johannesburg containing yet
more H. naledi bones, including the almost complete skeleton
of an adult male.
Narrowing down dates for the hominin fossils is remarkable
because many palaeontologists, including Berger, had believed that based on
their appearance, the bones were at least two million years old. If these
estimates had proven to be accurate, it would have placed H. naledi at the base of the
Homo genus as one of the oldest species in our family tree.
The dating issue became controversial because the first
bones were found in 2013 and presented to the public in 2015 without any
evidence for their age. Some professionals insinuated that the absence of a
reliable age for the bones showed that Berger and his team had rushed their
investigations.
After a long wait, Prof Paul Dirks and his team published a
paper this month in the online journal eLife
showing that the concentration of radioactive elements and the damage they caused
in three fossilized teeth mean that the fossils are most likely between 236,000
and 335,000 years old.
To ensure that the results were accurate, the paper confirms
that “the most crucial tests were carried out at independent laboratories
around the world, and the scientists conducted the tests without knowing the
results of the other laboratories”.
The fact that the Rising Star fossils are much younger than
had been expected does not necessarily mean that H. naledi should be removed
from the base of our family tree. It is possible that about 2.5 million years
ago, there was a fork in the original family of H. naledi where one part
evolved into H. erectus and eventually H. sapiens, while the other side
lingered on unchanged as H. naledi for another two million years or so.
While there is no evidence to support this possibility, it
cannot be ruled out. It is quite probable that H. naledi will turn out to
be an evolutionary dead-end – an interesting one – but nevertheless quite dead.
However, what is likely to be the most controversial aspect
of Berger’s announcement is his claim that “H. naledi possibly lived at the same time, and in
the same place, as modern humans”. This is the angle that led in most
mainstream publications in South Africa.
The Port Elizabeth Herald declared unequivocally that “Homo
Naledi lived with man” even though not a shred of evidence was presented to
support this dramatic claim. The newspaper said, “About 300 000 years ago‚
South Africans shared their land with another human-like species: Homo Naledi”.
This statement created erroneous impressions that first of
all, there were South Africans; and secondly that these South Africans lived in
harmony with relatives of another species. We can almost imagine them breaking
bread together and perhaps sharing a fraternal beer in the spirit of ubuntu.
News 24 online news site said, “scientists and researchers
can now reveal that it is highly likely that the species lived alongside Homo
sapiens” suggesting that they hung out together.
Even Wits Vice Chancellor Adam Habib got caught up in the
political feel-good spin conjured up by Berger and according to the Herald said “The true significance
of this research shows we belong to a common humanity. That is a fundamental
thing.
“In a world of division … when people are looking at their
ethnicity to define who gets what and in a world where we are becoming so
intolerant of each other‚ this research shows we have very common roots. We
represent a common humanity.”
Actually it doesn’t.
The real problem with portraying humans and H. naledi as best buds is that there is no evidence to
show that they were alive at the same time. If we take the youngest date for the
existence of H. naledi as being 236,000 years ago and the oldest date
for anatomically modern humans as being 200,000 years ago – there is quite a
large gap of around 36,000 years.
It is true that someone might find evidence to support the notion
that H. naledi is younger
or H. sapiens is older, but currently this possibility is not sustained. Things
might change, but in terms of current research, Berger is stretching the
boundaries of what might, conceivably be possible into the realm of what could
be good publicity for his book - which coincidentally was published on the same
day as his dramatic announcements.
