We thought that growing up defined the genus ‘Homo’ from its beginnings. Massive analysis proves we were wrong

For decades, paleoanthropology has tried to decipher at what exact moment in our family tree we took the big “growth spurt” in our height to go from being relatively small people to the heights we see today in our environment. The classical anatomical belief held that the appearance of our genus was accompanied by a drastic and immediate increase in body size, but little by little We are learning more exact details.

A new study recently published point out that the evolution of our body mass was not a sudden jump that defined all the first humans equally at the same moment, but rather a much more complex and gradual process than we thought.

What we believed. Traditionally, several evolutionary models suggested that the origin of the genus Homo marked an abrupt anatomical boundary. It was assumed that the first humans quickly developed bodies much larger than those of the australopithecines, thus justifying new locomotor and energetic adaptations for the new ‘functions’ that we would acquire on a daily basis.

To test these competing hypotheses, the research team has not simply compared fossil estimates in isolation, but has used advanced statistical tools on a data set composed of 386 specimens spanning 21 different taxa. This methodological rigor allows us not only to compare raw sizes, but also to take into account phylogenetic non-independence, size variation within the same species and the margins of uncertainty inherent to the fossil record itself.

When did we take the growth spurt? The results of the analysis are statistically conclusive and rewrite the previous consensus, since, contrary to the classic hypotheses, the researchers found very weak support for the idea that the increase in size was a defining and transversal characteristic of the entire genus. Homo.

Instead, the data show strong evidence that the marked increase in body mass occurred exclusively in species of Homo later, explicitly excluding the Homo habilis. That is, the first representatives of our genus continued to maintain a relatively modest size and the true biological leap that led us to scale our body proportions occurred later in the evolutionary lineage.

It wasn’t that simple. As New Scientist points out, understanding body size is essential to understanding our past. However, for scientific rigor, the article of PNAS It stands as the essential primary source compared to more generalist readings, since, while there are voices that tend to look for immediate “cause and effect” narratives, the strict biological data of this study demonstrate that human evolution rarely works with changes that occur overnight all at once.

That is why this work eliminates the “noise” of previous speculation by integrating multiple variables into a single analytical framework, and the result is that it was selective pressures and millions of years that modeled the physiology and size of the modern human being.

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