Neanderthals had a brain at birth of a similar size to that of modern-day babies. However, after birth, their brain grew more quickly than it does for Homo sapiens and became larger too. Nevertheless, the individual lifespan ran just as slowly as it does for modern human beings. These new insights into the history of human evolution are being presented this week in PNAS by researchers from the University of Zurich.
Dr. Marcia Ponce de León and Prof. Christoph Zollikofer from the Anthropological Institute of the University of Zurich examined the birth and the brain development of a newborn Neanderthal baby from the Mezmaiskaya Cave in the Crimea. That Neanderthal child, which died shortly after it was born, was evidently buried with such care that it was able to be recovered in good condition from the cave sediments of the Ice Age after resting for approximately 40,000 years.
The only well-preserved find of a fossil newborn known to date provides new information on how, in the course of evolution, the very special kind of individual human development has crystallised. Dr. Marcia Ponce de León and Prof. Zollikofer reconstructed the skeleton on the computer from 141 individual parts. They discovered that the brain at the time of birth was of exactly the same size as a typical human newborn. It had a volume of about 400 cubic centimetres. However, the skeleton was considerably more robustly formed than that of a modern human newborn.
In order to clarify whether the head of a Neanderthal newborn baby, like today's human, still fits through the birth canal of the mother's pelvis, they reconstructed a female Neanderthal pelvis which had already been found in the 1930s. This enabled the process of birth to be simulated. The computer reconstruction shows that the birth canal of this woman was wider than that of a Homo sapiens mother, but the head of the Neanderthal newborn was somewhat longer than that of a human newborn because of its relatively robust face. This meant that for the Neanderthals, the birth was probably about as difficult as it is for our own race.
"The brain size of a newborn of 400 cubic centimetres is probably an evolutionary birth limit which had already been reached with the last common ancestors of human beings and Neanderthals," concludes Zollikofer. "That would mean that for the last 500,000 years, we have been paying a high evolutionary price in the form of birth problems for our large brain."
To study the development after birth, the researchers examined not only the Mezmaiskaya newborn but also other Neanderthal children up to an age of approximately 4. It is astonishing that the Neanderthal brain grew even more quickly during childhood than that of Homo sapiens. Until now, one has assumed that the consequence of rapid growth was a shorter lifespan and high mortality under the motto of 'live fast – die young.'
However, the new studies show that the Neanderthal brain indeed grew more quickly than our own, but on average, a larger volume had to be reached in adult age. The duration of brain growth is therefore the same for both kinds of human being.
The large brain brought consequences for the life history (pregnancy, puberty, life expectancy) of the Neanderthals. For children to develop a large brain in a short space of time, they need additional energy and nutrition from the mothers. The only mothers capable of providing this were those who had developed the necessary constitution themselves. They therefore had their first child a little later.
If one now compares the entire life history of an average Neanderthal with that of a modern human being, a picture emerges which deviates significantly from existing doctrine: the development of the Neanderthals was just as slow as that of modern people, if not even a little slower.
Despite major physical differences between modern man and the Neanderthal since birth, both types actually obey the same restrictions which are forced upon us by the laws of physiology, development and evolution.
"As far as birth, development of the brain and life history are concerned, we are astonishingly similar to each other," says Dr. Ponce de León.
Article: Marcia S. Ponce de Leon, Lubov Golovanova, Vladimir Doronichev, Galina Romanova, Takeru Akazawa, Osamu Kondo, Hajime Ishida, and Christoph P. E. Zollikofer, 'Neanderthal brain size at birth provides insights into the evolution of human life history', PNAS: DOI: 10.1073/pnas.0803917105