This is the oldest fossil human protein ever sequenced. The research will be published the week of March 7-11 in the online early edition of Proceedings of the National Academy of Sciences (PNAS).
"This research opens up the possibility of getting detailed protein information from past human populations, to make inferences about the evolution of human diet and physiology," said Erik Trinkaus, Ph.D., the Mary Tileston Hemenway Professor of Physical Anthropology in Arts & Sciences at Washington University in St. Louis.
Trinkaus is considered by many to be the world's most influential scholar of Neanderthal biology and evolution. He conducted extensive field work at Shanidar Cave and is one of the paper's authors.
It is rare to recover a protein of this age and remarkable to be able to determine the amino acid sequence of this protein.
Protein sequences may be used in a similar way to DNA, to provide information on the genetic relationships between extinct and living species. As ancient DNA rarely survives, this new method opens up the possibility of determining these relationships in much older fossils which no longer contain DNA.
The research presents the sequence for the bone protein osteocalcin from a Neanderthal from Shandivar Cave as well as osteocalcin sequences from living primates (humans, chimpanzees, gorillas and orangutans). The team found that the Neanderthal sequence was the same as modern humans.
The team also found a marked difference in the sequences of Neanderthals, humans, chimpanzees and orangutans from that of gorillas and most other mammals. This sequence difference is at position ni ne where the amino acid hydroxyproline is replaced by proline.
The authors suggest that this is a dietary response, as the formation of hydoxyproline requires vitamin C, which is ample in the diets of herbivores like gorillas, but may be absent from the diets of the omnivorous primates such as humans and Neanderthals, orangutans and chimpanzees. Therefore, the ability to form proteins without the presence of vitamin C may have been an advantage to these primates if this nutrient was missing from their diets regularly.
This research opens up the exciting possibility of extracting and sequencing protein from other fossils, including earlier humans, as a means of determining the relationships between extinct and living species, and to better understand the phylogenetic relationships.