Our closest extinct relatives may have developed a very different growth trajectory from us. While modern humans follow a steady growth pattern, Neanderthals may have reached their physical and brain maturity much earlier in their lives, reports a newly published study.
“Neanderthals were different from Homo sapiens at a very young age, which means that the differences have [a] biological or genetic origin,” Ella Been, an anthropologist at Ono Academic College in Israel, told Refractor. “It's not only that the morphology is different, but the way they grew is different. They grew faster at a younger age.”
In 1992, anthropologists discovered a specimen, Amud 7, at Amud Cave in northern Israel. It's one of the most complete Neanderthal infant skeletons assigned to the age range of 6 to 14 months. Neanderthal infants are very rare, with only a few individual documentations, resulting in an obscure understanding of their growth and development. So, “it’s a good idea to study the skeleton of the baby,” Been says.
Been and her colleagues conducted an anatomical analysis of nearly 111 skeletal pieces recovered from the site, analyzing the infant's limb bones, vertebrae, pelvis, skull fragments, and teeth.
The team found discrepancies between the dental age and skeletal age. The analysis of enamel formation in the baby’s teeth estimated the histological dental age around 6 months. However, based on measurements of the long bones, Amud 7 was somewhere between 12 and 14 months old, compared to modern humans. “Dental age is the more accurate age,” Been told us.
That means that a 6-month-old Neanderthal baby was about the size of a young human toddler over a year old. The team observed a similar pattern when they compared data from several other Neanderthal infants.
Interestingly, while they grew faster than modern human children do, they did not end up bigger than Homo sapiens.
Been says that this rapid early growth is an evolutionary strategy to reduce the risk of hypothermia, i.e., losing heat faster than the body can produce it. Individuals with small bodies tend to be more susceptible to hypothermia than larger ones. Neanderthals evolved in Europe under cold conditions; they probably evolved this adaptive strategy to survive the harsh conditions of their environment.
However, this rapid growth pattern, researchers say, may have required more energy to support physical and brain development. The anthropologist told us that their mothers, or the group, had to ensure that the infant got enough calories. “But how did they get these calories? Were they breastfeeding? Were they eating by themselves? We have no idea,” she adds.
“I was surprised how much information you can get from bones that are over 50,000 years old of a little baby,” Been concludes.
The study has been published in Current Biology.
