New-born humans’ brains are about the same size and of similar appearance to those of Neanderthals, but alter in the first year of life, a new scientific study suggested.

The differences between our brains and those of our extinct relatives take shape mainly after birth and in the initial 12 months, a report in the Current Biology said.

The findings are based on comparisons of virtual imprints of the developing brain and surrounding structures, called endocasts, derived from the skulls of modern and fossilised humans, including that of a new-born Neanderthal.

Philipp Gunz of the Max Planck Institute for Evolutionary Anthropology, who undertook the study, said the differences researchers observed in early brain development were thought to reflect changes in the underlying brain circuitry. It is this internal organisation of the brain that matters most for cognitive ability.

He said: “In modern humans, the connections between diverse brain regions that are established in the first years of life are important for higher-order social, emotional and communication functions. It is therefore unlikely that Neanderthals saw the world as we do.”

Dr Gunz said the issue of whether cognitive differences exist between modern humans and Neanderthals is hotly debated in anthropology and archaeology.

Many researchers had assumed the cognitive capabilities of the two species were similar because the range of brain sizes in Neanderthals overlaps with humans. The new findings challenge that notion.

The elongated overall shape of the braincase has not changed much in the course of more than two million years of human evolution, despite a big increase in endocranium volume.

The new findings show that, at the time of birth, both Neanderthals and modern humans have elongated braincases, but only modern human endocasts change to a more globular shape in the first year of life.

Dr Gunz added: “The distinct globular braincase shape of adult humans is therefore largely the result of an early brain development phase that is absent from Neanderthals.”

The research team had earlier found the developmental patterns of chimpanzee and human brains are remarkably similar after the first year of life, but differ markedly immediately after birth.

According to the researchers, it might also shed light on the results of a recent comparison of Neanderthal and modern human genomes.

They speculate that a shift away from the ancestral pattern of brain development occurring in early Homo sapiens underlies brain reorganisation and that the cognitive differences made this growth pattern a target for positive selection in modern humans.