Friday, January 04, 2013

Human evolution: endurance running made our brains larger and smarter.

Gretchen Reynolds reviews work suggesting that our advanced cleverness and big brains may have come not from the need to think but becoming endurance athletes, able to bring down swifter prey through sheer doggedness, jogging and plodding along behind them until the animals dropped. It turns out our larger brain size with respect to body size is also shown to some extent by species like dogs and rats that have a high innate endurance capacity, presumably evolved over millennia. it is also seen in mice and rats systematically bred to be marathon runners. After multiple generations, these animals begin to develop innately higher levels of tissue growth and health promoters, including the protein brain-derived neurotrophic factor, or BDNF. These substances are important for endurance performance. They also are known to drive brain growth. Such observations have led Raichlen and Polk to suggest that physical activity may have helped to make early humans smarter:

The hunting and gathering lifestyle adopted by human ancestors around 2 Ma required a large increase in aerobic activity. High levels of physical activity altered the shape of the human body, enabling access to new food resources (e.g. animal protein) in a changing environment. Recent experimental work provides strong evidence that both acute bouts of exercise and long-term exercise training increase the size of brain components and improve cognitive performance in humans and other taxa. However, to date, researchers have not explored the possibility that the increases in aerobic capacity and physical activity that occurred during human evolution directly influenced the human brain. Here, we hypothesize that proximate mechanisms linking physical activity and neurobiology in living species may help to explain changes in brain size and cognitive function during human evolution. We review evidence that selection acting on endurance increased baseline neurotrophin and growth factor signalling (compounds responsible for both brain growth and for metabolic regulation during exercise) in some mammals, which in turn led to increased overall brain growth and development. This hypothesis suggests that a significant portion of human neurobiology evolved due to selection acting on features unrelated to cognitive performance.

1 comment:

Marc Verhaegen said...

From my recent paper in Human Evolution 28:237-266, 2013: “… The nowadays popular ideas about Pleistocene human ancestors running in open plains (‘endurance running’, ‘dogged pursuit of swifter animals’, ‘born to run’, ‘le singe coureur’, ‘Savannahstan’) are among the worst scientific hypotheses ever proposed. The surprising frequency and diversity of foot problems (e.g., hammertoes, hallux valgus and bunions, ingrown nails, heelspurs, athlete’s feet, corns and calluses—some of these due to wearing shoes) and the need to protect our feet with shoes prove that human feet are not made in the first place for running. Moreover, humans are physiologically ill-adapted to dry open milieus: ‘We have a water- and sodium-wasting cooling system of abundant sweat glands, totally unfit for a dry environment. Our maximal urine concentration is much too low for a savanna-dwelling mammal. We need much more water than other primates, and have to drink more often than savanna inhabitants, yet we cannot drink large quantities at a time” (Verhaegen 1987 “Origin of Hominid Bipedalism” Nature 325:305-6).”
Incredible that are still “scientsts” who believe this Pleistocene Homo running fantasy.

Human Evolution now publishes the proceedings of the symposium on human waterside evolution ‘Human Evolution: Past, Present & Future’ in London 8-10 May 2013:
SPECIAL EDITION PART 1 (end 2013)
Introduction – Peter Rhys-Evans
1. Human’s Association with Water Bodies: the ‘Exaggerated Diving Reflex’ and its Relationship with the Evolutionary Allometry of Human Pelvic and Brain Sizes – Stephen Oppenheimer
2. Human Ecological Breadth: Why Neither Savanna nor Aquatic Hypotheses can Hold Water – JH Langdon
3. Endurance Running versus Underwater Foraging: an Anatomical and Palaeoecological Perspective – Stephen Munro
4. Wading Hypotheses of the Origin of Human Bipedalism – Algis Kuliukas
5. The Aquatic Ape Evolves: Common Misconceptions and Unproven Assumptions about the So-Called Aquatic Ape Hypothesis – Marc Verhaegen
6. The Epigenetic Emergence of Culture at the Coastline: Interaction of Genes, Nutrition, Environment and Demography – CL Broadhurst & Michael Crawford
SPECIAL EDITION PART 2 (begin 2014) with 12 contributions

Post a Comment