Over the course of human evolution our bodies changed a lot. We began walking upright, we grew big brains and even got a bit chubby. New research into hominin body size also reveals we got very tall as well. Now, this isn't because we're particularly gargantuan (with a comparable body mass to chimps) but because our ancestors were a lot smaller than we thought.
The fact our ancestors were small is hardly a new discovery. Most of you have probably seen a picture of the famous Lucy fossil (and if you haven't look next to this paragraph). However, most of these images don't give you anything to compare it to. It's easy to miss that - at just over a meter tall - she wouldn't come up to most people's chest.
However, this new review of hominin body size reveals that just looking at height doesn't capture the whole picture. They also examined the body mass of our family and found hominins were very skinny as well as rather small. The researchers used more than 200 modern humans to reconstruct the bodies of more 90 fossil hominins. This wasn't the first time this has been done, but it is the largest (and thus most reliable) review of its kind.
These results show that hominin body size was lower than previously thought. For example, Homo habilis - the first member of our genus - came out as weighing ~32 kg. That's almost 10kg lighter than the previous best estimate.
But the most interesting finding of this research wasn't how much smaller hominin body size was; but how early that seemed to change. By examining so many more fossils than previous studies, the researchers were able to find examples of early chubby species. Lucy's species, for example, came out several kilograms heavier than previous estimates.
The shift to a larger body was important for human evolution. Longer legs, for example, increased our stride length making walking much more efficient. It was previously thought that this shift towards the modern human body occurred relatively late, perhaps in Homo habilis or Homo erectus. However, this new re-evaluation of hominin body size suggests it may have gotten started much earlier. Lucy's species shows evidence of taking those first fateful steps towards the modern body we now have.
