A study published by German anthropologists reveals how, in the first year of life, new-born Neanderthals and human babies had remarkably similar brains.
Neanderthals saw things differently to humans
The research, conducted by a team from the Leipzig-based Max Planck Institute for Evolutionary Anthropology, found that infant Neanderthals had brains not only the same size as, but almost identical to those of modern-day babies.
But not for long. As researcher Philipp Gunz explained to Deutsche Welle, the similarities evolved into differences during the first year of their lives, a finding which proves a cognitive gulf between humans and the extinct species.
"What is being established during that period, both in humans and Neanderthals, is synaptic connection among brain cells," Gunz said. "We know from the example of modern man that even subtle differences can have significant consequences on development, and can contribute to social and communication skills."
And although Gunz says there is little doubt that the Neanderthals, which have been extinct for almost 30,000 years, had language and did communicate with each other, they would have seen the world differently to the way we do.
Same, same, but not for long
How alike were we really?
Baby Homo neanderthalensis' elongated braincases – also found in new-born humans – had more to do with the physical make-up of the mothers than anything else.
"The baby has to fit through the birth canal and the shape of both was very similar so that would impose a constraint."
But once unbridled and free to grow at will, human braincases gradually begin to change form to become more globular. It is this shape which Gunz believes proves early brain development in man which is absent in Neanderthals.
In earlier research the scientists discovered that right after birth human brains are quite unlike those of chimpanzees, but that they become more similar at a later stage of development. This shows that the "globularization phase" sets humans apart from both chimps and Neanderthals.
Chimps and man: not so similar
"We think modern humans, chimpanzees and Neanderthals share one ancestral growth pattern that that goes back millions of years," Gunz continued. "But in the first year of life, modern humans depart from this ancestral pattern."
And contrary to past opinion, it is this first year, and not brain size, which is crucial to cognitive development. The Leipzig anthropologists say it is the internal organization of the brain that matters.
What's in an ancient tooth?
The scientists hope their research will help them understand a little more about the function of the genes, only a very small number of which separate modern humans from their extinct counterparts.
"We assume that some of these genes are related to brain development," Gunz said. "In living people these mutations are linked to autism or schizophrenia or down-syndrome."
And while he is not suggesting that an autistic child is a throwback to tens of thousands of years ago, the Leipzig anthropologist does venture a link.
"We know from teeth that Neanderthals grew faster, so maybe some of the genes are related to the regulation of brain growth."
Reporter: Tamsin Walker
Editor: Nathan Witkop