A new study casts doubt on the role of natural selection in brain growth and facial shrinkage. It appears that random mutations and cultural changes, such as tool development, played a pivotal role in these evolutionary shifts.
Nature Communications reported that researchers from the Universities of Tennessee and Tübingen studied how the appearance of human ancestors changed over millions of years.
The prevailing scientific view assumes that brain growth and facial and jaw shrinkage in members of the human race (Homo) resulted from natural selection, as a larger brain provides better cognitive abilities, while a smaller face contributes to reducing energy consumption.
However, the new study casts doubt on this hypothesis. The researchers analyzed three-dimensional measurements of 87 fossil skulls belonging to different species, from Homo habilis to Neanderthals and modern humans, covering a period of time spanning about two million years, providing a comprehensive database for analyzing evolutionary patternse
The research team compared the observed changes with several evolutionary models, including natural selection, neutral evolution, and the "punctual equilibrium" model, which posits alternating periods of long stability with short periods of rapid change. The results showed that neutral evolutionary processes and long periods of stability better explain changes in skull shape than natural selection alone
Researchers believe that random mutations, biological constraints, and environmental stability may have played a more important role than previously thought, compared to changes that confer direct evolutionary advantages
The study also indicates that cultural development has had a significant impact on the course of human evolution, as new technologies and methods of obtaining food have helped to reduce physical strain and meet the demands of a larger brain. For example, the development of tools may have reduced the need for strong jaws.
The study concludes that human evolution is a complex process shaped by the interaction of random mutations, biological constraints, environmental factors, and cultural progress, prompting researchers to focus on the conditions that allowed these changes to occur, rather than searching for a single cause behind them.
