Ida, The Missing Link?

The Independent news story on a recently publicized fossil (it was discovered 26 years ago) insists it's not the missing link between homo sapiens and earlier primates. True or not, it sounds like a fantastic find from which scientists are learning a lot. Indications are that it is very likely genuine and not a hoax. Hard to believe, given how well preserved it was when found, but after more than a year of tests the evidence is pretty good.

What is so special about the fossil?

There are several features that make Ida stand out, other than the almost miraculous preservation of about 95 per cent of its skeleton. The first striking anatomical feature – other than the absence of a penis bone or bacculum, making Ida unmistakably female – is the animal's opposable thumbs, which she used for climbing trees and picking up items of food such as berries and fruit. Opposable thumbs on a five-digit hand are a signature feature of monkeys and apes and were essential for the precision grip needed to make and handle tools, a key development in human evolution.

What else have we learnt about her?

Other anatomical features include the presence of a distinctive ankle "talus" bone in Ida's foot, another link to human anatomy. Only the human talus is obviously bigger, according the Natural History Museum at the University of Oslo, which was involved in the scientific analysis of the fossil. Further interesting features of its anatomy are the absence of a "toothcomb", a fused row of teeth in the middle of the lower jaw, and a "toilet claw", a grooming claw on the second digit of the foot. These features are attributes of lemurs but absent in monkeys and apes, indicating Ida's transition to anthropoid primates.

Furthermore, Ida's fingertips end in nails rather than claws, which is another link with monkeys and apes. Her eye sockets housed large, forward-pointing eyes that probably gave her good 3-D, binocular vision. Her big eyes would have been useful for a lifestyle of night-time foraging.

Amazing stuff, evolution...