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Neanderthal Brain Size at Birth Sheds Light on Human Evolution

Neanderthal-one.jpg

Three-dimensional computer-assisted reconstructions of Neanderthal infants based on fossils found in Russia and Syria (left) suggests that our closest human relatives had brains as large as ours at birth and larger than ours as adults.

The finding indicates that we and the Neanderthals inherited the pattern of early brain size and development from a yet unknown common human ancestor, researchers who did the reconstruction say. Still largely unknown is how this pattern of brain development arose during evolution.

The research also sheds light on the similarities and differences in the life histories of modern humans and Neanderthals: the timing of major events in an individual’s life, such as gestation time, age at sexual maturity, and age at death. The differences could have given modern humans an evolutionary advantage, the study indicates.

Image courtesy of M. Ponce de León and C. Zollikofer, University of Zurich

“Compared to our closest living relatives, the chimpanzees, we have a peculiar style of development. Our newborns have an exceptionally large brain (400 cubic centimeters, like an adult chimp), which makes birth a difficult process,” University of Zurich scientists Marcia Ponce de León and Christoph Zollikofer said in notes accompanying a paper published today in the Proceedings of the National Academies of Science.

Virtually nothing has been known about birth and early brain development in our fossil human relatives and ancestors, according to the researchers. “This is mainly because fossil remains of very young individuals are extremely rare and difficult to reconstruct, because skeletal ossification is still incomplete.”

In their paper, the researchers investigated birth and early brain development in the Neanderthals. They used computerized reconstruction to recover the morphology of the youngest known Neanderthal individuals: a newborn from Mezmaiskaya Cave (Crimea, Russia), and two infants from Dederiyeh Cave (Syria) with individual ages of 19 and 24 months at death, respectively. They also recomposed a fragmentary female Neanderthal pelvis from Tabun Cave (Israel).

Together, these individuals provide new insights into “Neanderthal obstetrics” as well as patterns of brain growth and the evolution of human life history, they said.

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The computerized reconstruction shown here is based on the fossil remains of a one-week-old Neanderthal from Russia and an adult female from Israel. Reconstruction of the birth process in Neanderthals shows that newborns of this extinct human species had similarly large brains as modern human newborns, probably causing similar difficulties with childbirth as with our own species, scientists said.

 Image courtesy of M. Ponce de León and C. Zollikofer, University of Zurich

What, according to the researchers, are some of the most relevant findings of the paper?

Neanderthals were different from modern humans already at birth. This implies that most species-specific characteristics such as the Neanderthal’s heavy brow developed during embryonic and fetal development, rather than after birth.

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Brain size at birth, a typically human feature, appears to be an old evolutionary achievement, inherited from a common ancestor.

Neanderthal women had to face similar child-bearing problems as modern human women. The female Neanderthal pelvis was wider than in modern human females–but the head size of Neanderthal newborns was also larger.

After birth, Neanderthal brains grew faster than those of modern humans, but they had to reach larger adult brain sizes. Faster growth did not imply earlier completion of growth, the scientists said.

Illustration of Neanderthals by Charles R. Knight/NGS

Growing large brains at a fast pace is an energy-intensive process, which can only be sustained by large, late-maturing mothers.”Compared to modern humans, it thus appears that Neanderthals had somewhat slower life histories,” the researchers said. This meant they reached sexual maturity later and may have lived longer.

The slow life history of the Neanderthals might be a feature shared with Ice Age populations of Homo sapiens. These early modern humans had larger adult brain sizes than people today.

“Brain size reduction in modern humans over the past 40,000 years is well-documented,” the researchers said in their notes. “We hypothesize that growing smaller but similarly efficient brains might have represented an energetic advantage, which paid off in faster reproductive rates in modern [humans] compared to Pleistocene people. Reducing brain size thus might represent an evolutionary advantage.”

Read the National Geographic News story about this paper:

Neanderthals Grew Fast, but Sexual Maturity Came Late

Comments

  1. Bob
    England
    July 19, 2013, 4:20 pm

    Great website

  2. Vijay
    Las Vegas
    March 13, 2013, 3:42 am

    Supposedly they lived longer, had larger brains, and humans are an example of onwards and upwards evolution from this? That doesnt make sense. The Biblical explanation does though. This is appreciated.

  3. navid
    November 20, 2012, 1:07 pm

    I want exact different between neanderthal brain and modern brain.
    Thanks for good website.

  4. camila
    Stamford, CT 06902
    October 3, 2011, 8:25 pm

    This is a really good website but it needs more information like what was the brain size of a Neanderthal in ml or CC as they say now. i had a project on October 3, 11 and i went to this website but you didn’t give the size of a Neanderthal. But, for a positive way, Excellent Job!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! :)

  5. CanaBoo
    Asheville, NC
    May 4, 2011, 8:05 pm

    This really helped with a big science project. Thanks! (: