Wed. Apr 24th, 2019

New species, old mystery | Science

New species, old mystery | Science



For a twentieth-century paleontologist, the holy grail was to find the "missing link". The dominant theory was that human evolution drew a linear ascent from our humble ape-like ancestors, rising step by step to acquire the erect position and the articulated word that characterizes us now. Some intermediate steps were known - Neanderthal,Homo erectus', Australopithecus- and all that remained was to fill in the gaps: the missing links of a long and monotonous chain. But evolution rarely works like this. It usually has the shape of a tree, and the new Homo luzonensis It is the last branch that puts it in evidence. An already extinct branch, like all the others that, until about 50,000 years ago, shared the planet with us, the Homo sapiens.

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The small, primitive feet of 'Homo luzonensis' can only be explained in two ways. And the second contradicts all the previous evidence

For the rest, everything that surrounds the new species found in the Philippines it only deepens the mystery. The fossil treasure consists at the moment in seven teeth, three bones of the foot, two of the hand and a broken femur. There is no skull, so we do not know his brain capacity and, as the femur is broken, you can not calculate his height reliably (one and a half meters is the best guess). The bones, which come from two adults and a child, reveal that the man from Luzon was a mosaic of primitive and modern features. The teeth are small, as in our species-hence their classification in the genus Homo-but their hands and feet are more similar to those of the primitive australopithecines, with a curved shape that seems adapted to the arboreal life. This mixture of disparate traits reminds us of the Homo floresiensis (nicknamed the Hobbit), another mysterious species found in 2004, also in Southeast Asia. But that's where the similarity ends: the Flores species and the Luzón species are clearly different.

There are two alternative hypotheses about the origin of the man from Luzon. The first, which was already raised in the case of Hobbit, is that it is a Homo erectus miniaturized on the island of Luzon. The Homo erectus, according to all the evidence, it was the first human species that left Africa, two million years ago, and its presence in South Asia is well documented. And it is also known that islands can accelerate evolution. Miniaturization, for example, may be due to the fact that the main predators have remained on the continent, and there is no longer a reason to maintain a large and expensive size in terms of energy. More generally, small and isolated populations tend to change by mere genetic drift, and that could explain the return to primitive feet.

The second hypothesis is more shocking if possible. The man from Luzon would not come from Homo erectus, but of an Australopithecus. That would explain immediately that his feet are primitive, but it would imply that it was the old Australopithecus, and not the modern one. Homo erectus, the first to leave Africa, which contradicts all the previous evidence.

There is only one way to decide between the two: find more fossils. If possible, with a pinch of DNA.

* THE SCIENCE OF THE WEEK is a space in which Javier Sampedro analyzes scientific news. Subscribe to the Materia newsletter and you will receive it every Saturday in your email, along with a selection of our best news of the week.

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