Height, weight of our ancestors evolved at varying speed: Study

London, Nov 8 (IANS) The stature and body mass of hominins has evolved with varying speed, suggests a recent study involving fossils of 311 species spanning over four million years ago of humans who lived after the last ice age.

The study conducted by University of Cambridge stated that rather than steadily increasing in size, hominin bodies advanced in "pulse and stasis fluctuations", with some "lineages even shrinking".

For a long span, the height and weight of hominins evolved roughly in concert, nearly 1.5 million years ago, their stature separated from weight, and then the early humans went through a tall and skinny phase.

"An increase solely in stature would have created a leaner physique, with long legs and narrow hips and shoulders. This may have been an adaptation to new environments and endurance hunting, as early Homo species left the forests and moved on to more arid African savannahs," lead author Manuel Will from the University of Cambridge, said.

"The later addition of body mass coincides with ever-increasing migrations into higher latitudes, where a bulkier body would be better suited for thermoregulation in colder Eurasian climates," he added.

The study published in the journal Royal Society Open Science also stated that the scientists identified three key "pulses" of significant change. The first change occurred with Homo around 2.2-1.9m years ago and saw a joint surge in both height (around 20 cm) and weight (between 15-20kg). Stature then separated from heft with a height increase alone of 10cm between 1.4-1.6m years ago, shortly after the emergence of Homo erectus. Consistently heavier hominins with an estimated 10-15kg greater body mass began appearing in the fossil record only a million years later (0.5-0.4m years ago).

"Body size is one of the most important determinants of the biology of every organism on the planet," Will said.

"Reconstructing the evolutionary history of body size has the potential to provide us the insights into the development of locomotion, brain complexity, feeding strategies, and even social life," he noted.

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