DNA analysis of ancient humans poses more questions than answers

DNA analysis of 400,000 year old bones found in Spain, the oldest known human remains, has yielded more questions than answers. The human family tree is now thought to have had many more branches than previously thought after the analysis which was the first time scientists could gain data from this period.

Originally it was thought the bones may have been Neanderthal but instead the bones have a closer relationship to Denisovans, a distinct human sub-species who lived in Siberia. The Denisovans interbred with the Neanderthals and Modern Humans, bones from the other human species found alongside their's, and traces of their DNA remains in humans today. Around 6% of the DNA in Melanesian people (living in places like Papua New Guinea) is shared with the Denisovans. Indeed around 4% of the DNA in non-Africans is Neanderthal.

Say hello to our earliest ancestor?

Fifty five million years ago in the palaeocene there lived a small mammal (which is now called Archicebus achilles) in what is now China. It may be this is the earliest known primate and thus the common ancestor to monkeys, apes and us!

Archicebus was rather small, being only 7cm long, and lived alongside tropical lake shores eating insects. The fossils of Archicebus show features now known in tarsiers, early primates which now live in South East Asia. Other features are common in other primate groups.

Near complete skeletons of Archicebus are known which is greatly aiding analysis. Archicebus lived about 7 million years earlier than the previous earliest known primates. Archicebus may also show the divergence point between tarsiers and modern monkeys and apes, a key point in human evolution.

Aurornis xui beats Archaeopteryx as earliest bird?

The discovery of a fossil of Archaeopteryx in 1861 was one of the greatest fossil discoveries ever. The fossil showed the earliest known (at the time) bird and also a transitionary stage in the evolution of a branch of reptiles into birds, helping illustrate Darwin's theory of evolution too. Now finally an earlier stage in that evolution has been found.

Aurornis xui predates Archaeopteryx by 10 million years in the Jurassic period (about 150 million years ago). It shares many of the other early bird's features such as a long tail but is considered more primitive and the most primitive avian yet discovered. The fossil has preserved the outline of feathers along the body and tail though Aurornis was unlikely to have been able to fly.

Some scientists are not convinced Aurornis should be classified as a "bird" but rather was still a reptile but all agree it provides an important step in the evolution of the birds. Interestingly the discovery of Aurornis helps re-establish Archaeopteryx in the bird family tree after some scientists relegated it to a class of winged dinosaurs.