Hominin is the group consisting of modern humans, extinct human species and all our immediate ancestors. Almost all of the hows and whys of human evolution are tied to estimates of body size at particular points in time.
Challenging prevalent theories, a new study suggests that the earliest members of the Homo genus (which includes our Homo sapiens species) may not have been larger than their ancestors in the hominin species.
But the new study challenge numerous adaptive hypotheses based around the idea that the origins of Homo coincided with, or were driven by, an increase in body mass.
"One of our major results is that we found no evidence that the earliest members of our genus differed in body mass from earlier australopiths (some of the earliest species of hominins)," said one of the researchers Mark Grabowski, assistant research professor at George Washington University in the US.
"In other words, the factors that set our lineage apart from our earlier ancestors were unrelated to an increase in body size, which has been the linchpin of numerous adaptive hypotheses on the origins of our genus," Grabowski noted.
Produced using cutting-edge methodology and the largest sample of individual early hominin fossils available, the study showed that early hominins were generally smaller than previously thought and that the increase in body size occurred later with H. erectus (the first species widely found outside of Africa).
The study was published online in the Journal of Human Evolution