It’s no secret
that regular exercise maintains and improves a person’s internal and external fitness,
but new hypotheses, discussed in a recent article by The New York Times, are
emerging concerning the extent of advantages that exercise can bring – and may
have already brought – to the human body. Walking is one of the key traits that
researchers in the past have used as evidence for human evolution, acquired
after human ancestors diverged from the ape lineage. Usually, their diet and collaborations
with others to hunt for food are the factors used to explain how humans
continued to evolve, but now, researchers suggest that endurance running could
have also had a major impact in how humans changed over time (Bramble and
Lieberman, 2004).
In
their paper, Dennis Bramble and Daniel Lieberman discuss how humans’ ability to
endurance run – and do so with relative ease – is impressively much greater
than any other comparable quadrupeds. Humans use much more metabolic energy while
endurance running in comparison to other mammals; biomechanical research within
humans today shows that their skeletons, long tendons in the legs, core
stability, and ability to maintain a regular body temperature would have made
running easier (Bramble et. al, 2004) and increased their chance of selection
for future generations. But how does endurance running relate to human evolution?
Bramble and Lieberman suggest that the ability to endurance run would have made
it easier for early, scavenging hominids to gain access to prey. As hominids
evolved into hunters and gatherers, endurance running capability grew more
important. As with early hominids, those who were able to outrun (and catch)
prey the longest, were more likely to be able to support their protein-rich
diet, survive longer, and be more successful in passing on their genes to the
next generation (Reynolds, 2012). However, these suggestions still don’t speak
as clearly to how exercise may have aided human evolution in the past.
In
another paper referenced by The Times, researchers David Raichlen and John
Polk discuss the link between endurance running in human ancestors and the
evolution of the brain. In line with the fact that humans can run longer than
other comparable quadrupeds, we also boast brains that are three times larger
than expected (Raichlen and Gordon, 2011). In recent studies, improved acuity
and an increase in specific areas of the brain were linked with extended exercise.
From experiments in rodents subjected to long bouts of aerobic activity,
researchers saw a significant increase in brain-derived neurotrophic factor
(BDNF), a protein that fosters brain growth and development. Other proteins
such as insulin-like growth factor I (IGF I) and vascular endothelial growth
factor (VEGF) also contribute to brain growth.
Figure from Raichlen & Polk, 2013: “Evolutionary model linking APA and brain size in humans. Solid
arrows denote downstream effects of selection for APA performance. Dashed arrow
indicates a possible adaptive link between neurobiology and exercise
performance.”
All
these experiments and research suggest that as early humans ran for long
periods of time after their prey, they were also slowly contributing to the
evolution of the brain, shifting the species into a more streamlined and
intelligent one than before. The long periods of aerobic exercise would have
not only increased their fitness so that those genes could pass on to
subsequent generations, but would have also increased proteins in the body that
allowed the brain to grow. As the brain grew, humans became more cognizant and
intelligent concerning increasingly complex matters.
So
for those looking for encouragement in keeping up with their new exercise
regimens, researcher Daniel Lieberman is correct when he says “there is a deep
evolutionary basis for the relationship between a healthy body and a healthy
mind” (Reynolds, 2012).
577 words
Cited Sources:
Bramble, D.M.,
& Lieberman, D.E. (2004 November 18). Endurance Running and the
Evolution
of Homo. Nature, 432(7015), p. 345-48.
doi:http://dx.doi.org.ezproxy.rice.edu/10.1038/nature03052
Raichlen, D.A.,
& Gordon, A.D. (2011 June 22). Relationship between Exercise Capacity
and
Brain Size in Mammals. PLos One,
6(6).
doi:10.1371/journal.pone.0020601
Raichlen,
D.A., & Polk, J.D. (2013 January 7). Linking brains and brawn: exercise and
the
evolution of human neurobiology. Proceedings of the Royal Society B, 280(1750).
doi:10.1098/rspb.2012.2250
Reynolds, G.
(2012 December 26). Exercise and the Ever-Smarter Human Brain. The
New York Times. Retrieved from http://well.blogs.nytimes.com/2012/12/26/exercise-and-the-ever-smarter-human-brain/.
