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Did we evolve to run?

StacyHackner5 January 2015

By Stacy Hackner

A few years ago, spurred by my research on just how deleterious the sedentary lifestyle of a student can be on one’s health, I decided to start running. Slowly at first, then building up longer distances with greater efficiency. A few months ago, I ran a half-marathon. At the end, exhausted and depleted, I wondered: why can we do this? Why do we do this? What makes humans want to run ridiculous distances? A half-marathon isn’t even the start – there are people who do full marathons back-to-back, ultra-marathons of 50 miles or more, and occasionally one amazing individual like Zoe Romano, who surpassed all expectations and ran across the US and then ran the Tour de France.[i] Yes, ran is the correct verb – not cycled.

I’ve met so many people who tell me they can’t run. They’re too ungainly, their bums are wobbly, they’re worried about their knees, they’re too out of shape. Evolution argues otherwise. There are a number of researchers investigating the evolutionary trends for humans to be efficient runners, arguing that we are all biomechanically equipped to run (wobbly bums or not). If you have any question whether you can or can not run, just check out the categories of races in the Paralympic Games. For example, the T-35 athletics classification is for athletes with impairments in ability to control their muscles; in 2012, Iiuri Tsaruk set a world record for the 200m at 25.86s, which is only 6 seconds off Bolt’s world record at 19.19 and 4 seconds off Flo-Jo’s womens record (doping aside). 2012 also saw the world record for an athlete with visual impairment: Assia El Hannouni ran 200m in 24.46.[ii] You try running that fast. Now try running with significant difficulty controlling your limbs or seeing. If you’re impressed, think about these athletes the next time you say you can’t run.

Paralympic_athlete

Paralympian Scott Rearden. Wikimedia Commons.

Let’s think about bipedalism for a bit. Which other animals walk on two legs besides us? Birds, for a start, although flight is usually the primary mode of transport for all except penguins and ostriches. On the ground, birds are more likely to hop quickly than to walk or run. Kangaroos also hop. Apes are able to walk bipedally, but normally use their arms as well. Cockroaches and lizards can get some speed over short distances by running on their back legs. However, humans are different as we always walk on two legs, keep the trunk erect rather than bending forward as apes do, keep the entire body relatively still, and use less energy due to stored kinetic energy in the tendons during the gait.[iii] Apparently we can group our species of strange hairless apes into the category “really weird sorts of locomotion” along with kangaroos and ostriches.

Following this logic, Lieberman et al point out that a human could be bested in a fight with a chimp based on pure strength and agility, can easily be outrun by a horse or a cheetah in a 100m race, and have no claws or sharp teeth: “we are weak, slow, and awkward creatures.”[iv] We do have two strokes in our favor, though – enhanced cognitive capabilities and the ability to run really long distances. Our being awkwardly bipedal naked apes actually helps more than one would think. First, bipedalism decouples breathing from stride. Imagine a quadruped running – as the legs come together in a gallop, the back arches and forces the lungs to exhale like a bellows. Since humans are upright, the motion of our legs doesn’t necessarily affect our breathing pattern. Second, we sweat in order to cool down during physical exertion. (In particular, I sweat loads.) Panting is the most effective way for a hairy animal to cool down, as hair or fur traps sweat and doesn’t allow for effective convection (imagine standing in a cool breeze while covered in sweat – this doesn’t work for a dog.) But it’s impossible to pant while running. So not only are humans able to regulate breathing at speed, but we can cool down without stopping for breath.

From a purely skeletal perspective, there is more evidence for the evolution of running. Human heads are stabilized via the nuchal ligament in the neck, which is present only in species that run (and some with particularly large heads), and we have a complex vestibular system that becomes immediately activated to ensure stability while running. The insertion on the calcaneus (heel bone) for the Achilles tendon is long in humans, increasing the spring action of the Achilles.[v] Humans have relatively long legs and a huge gluteus maximus muscle (the source of the wobbly bum). All of these changes are seen in Homo erectus, which evolved 1.9 million years ago.[vi]

H. erectus skeleton with adaptations for running (r) and walking (w). From Lieberman 2010.

H. erectus skeleton with adaptations for running (r) and walking (w). From Lieberman 2010.

The evolutionary explanation for this is the concept of endurance or persistence hunting. In a hot climate, ancient Homo could theoretically run an animal to death by inducing hyperthermia. This is also where we come full circle and bring in the cognitive capabilities of group work. A single individual can’t chase an antelope until it expires from heat stroke because it’ll keep going back into the herd and then the herd will scatter. But a team of persistence hunters can. If persistence hunting is how humans (or other Homo species) evolved to be great at long distance running, that’s also the why humans developed larger brains: the calories in meat generated an excess of calories that allowed nourishment of the great energy-suck that is the brain. However, persistence hunting is a skill that mostly went by the wayside as soon as projectile weapons (arrowheads and spears) were invented, possibly around 300,000 years ago. Why? Because humans, due to our large brains, are very inventive, but also very lazy. Any expenditure of energy must be made up for by calories consumed later, at least in a hunting and gathering environment – so less energy output means less energy input; a metabolic balance. Thus we have the reason why humans can run, but also why we don’t really want to. (As an aside, some groups such as the Kalahari Bushmen practiced persistence hunting until recently, although they had projectile weapon technology, probably because of skill traditions and retaining cultural practices. Humans are always confounding like that.)

Which brings up another point: gathering. As I’ve written before, contemporary hunter-gatherers like the Hadza rely much more on gathering than hunting. Additionally, it is possible that the first meat eaten by Homo species was scavenged rather than hunted. There is no such evolutionary argument as endurance gathering. If ancient humans spent much more time gathering, why would we evolve these particular running mechanisms? As with many queries into human evolution, these questions have yet to be answered. Either way, it’s clear that humans have a unique ability. Your wobbly bum is, in fact, the key to your running. Another remaining question is why we still have the desire to continue running these ridiculous distances – a topic for a future post, perhaps.

Sources

[i] http://www.zoegoesrunning.com

[ii] Check out all the records at http://www.paralympic.org/results/historical

[iii] Alexander, RM. Bipedal Animals, and their differences from humans. J Anat, May 2004: 204(5), 321-330.

[iv] Lieberman, DE, Bramble, DM, Raichlen, DA, Shea, JJ. 2009. Brains, Brawn, and the Evolution of Human Endurance Running Capabilities. In The First Humans – Origins and Early Evolution of the Genus Homo (Grine, FE, Fleagle, JG, Leakey, RE, eds.) New York: Springer, pp 77-98.

[v] Raichlen, DA, Armstrong, H, Lieberman, DE. 2011. Calcaneus length determines running economy: implications for endurance running performance in modern humans and Neandertals. J Human Evol 60(3): 299-308.

[vi] Lieberman, DE. 2010. Four Legs Good, Two Legs Fortuitous: Brains, Brawn, and the Evolution of Human Bipedalism. In In the Light of Evolution (Jonathan B Losos, ed.) Greenwood Village, CO: Roberts & Co, pp 55-71.

Mythical Hybrids and Fantastic Beasts

GemmaAngel13 May 2013

Gemma Angelby Gemma Angel

 

 

 

 

 

I’m going to describe a creature, and you have to try and guess what it is, based on the following three clues: 1) it lays eggs; 2) it has venomous claws; and 3) it uses electroreception to assist it in catching prey under water. You probably guessed some sort of reptile, right? Wrong. Ok, so those questions were a bit tricky. I’ll give you another three clues: 4) it’s semi-aquatic; 5) it has thick fur; and 6) despite laying eggs, it suckles its young on milk. Some of you will probably have worked out what this mysterious animal is by now. I am, of course, describing Ornithorhynchus anatinus, or as it is more commonly known, the platypus.

Growing up in Australia, I was fascinated by the native wildlife. As a curious 7-year-old recently emigrated from England, I tried to assimilate the unfamiliar Antipodean fauna into my limited understanding of the animal kingdom, largely through approximations: To me, the wombat was like a kind of stout, snub-nosed badger; sugar gliders were reminiscent of squirrels; and the echidna was a larger and longer-nosed version of the hedgehog. Kangaroos were a more difficult species to accommodate, with a face similar to a deer, and the hind legs of some sort of giant Alice-in-Wonderlandesque rabbit. But my system completely fell down when it came to the platypus. This creature was truly weird, a kind of animal cut-and-paste that defied all of the categories that I tried to fit it into. As it turned out, I wasn’t alone in my estimations of this remarkable and unique creature.

Platypus-sketch

Ornithornhynchus anatinus, John Gould (1863).

As an Australian native, the platypus has been known in Aboriginal culture for millennia – but it was not until 1797 that Europeans first encountered them. Captain John Hunter of the Royal Navy sent a pelt and a sketch back to Britain in 1798, [1] but the bizarre appearance of the creature baffled European naturalists. Some considered it to be an elaborate hoax, and Scottish zoologist Robert Knox believed the creature to be the work of an inventive Asian taxidermist. Even George Shaw, the first man to scientifically describe the platypus, admitted that “a degree of scepticism is not only pardonable, but laudable … I almost doubt the testimony of my own eyes.” [2]

Whilst it makes perfect sense that European observers would find the platypus strange, having never encountered anything like it in the Northern hemisphere outside of the bizarre chimerical creatures of mythology, it is perhaps more surprising that Aboriginal Dreamtime legends also describe the platypus as a peculiar exception within the animal realm. Known as the ‘mallangong’, tambreet’ or ‘duliawarung’ to local indigenous peoples, Aboriginal story-telling traditions use myth to explain the unique appearance and behavioural characteristics of the platypus. The platypus was believed to be the offspring of a mother duck and a father water rat, accounting for its unusual characteristics – inheriting the duck-bill, webbed feet and egg-laying abilities of their mother, and the thick fur, claws and four legs of their father. In an origin story of the platypus from Northern New South Wales, their poor mother Gaygar is ostracized by the other ducks because of her bizarre-looking hatchlings, and is forced to leave her home on Narran Lake. She takes her babies up into the Warrumbungle mountains, thereby accounting for why platypus are only found in particular regions. In another story from the New South Wales Central Coast, the animals argue amongst themselves about who is the most important creature. They form three exclusive groups, all convinced of their superiority: The animals with fur who can run across land, the birds who lay eggs, and the water creatures who can swim. All of the groups want the platypus to join them, since he shares characteristics with all of them, and each faction invites him to be part of their group. After thinking about this for some days, the platypus gathers all the animals to tell them his decision:

I don’t have to join anyone’s group to be special because I am special in my own way. Because I have fur and love to run across the land, I have a little bit of animal in me. I also have a little bit of bird in me because of my bill and the fact that my wife lays eggs. As well, I also have a bit of water creature in me because I love to swim and explore the underwater world. […] I don’t know why the ancestors have made us all different, but we must learn to accept these differences and live with each other. [3]

All of the animals listening, including people, agreed that the platypus was very wise; and the people decided that they would not hunt the platypus because he was so special. Non-human animal hybrids of Eurasian mythology have also often been considered special, such as the Griffin, which combined features of the lion and eagle, both of which were regarded as especially regal animals.

Animal-hybrids from diverse mythological traditions demonstrate the significance of animals within human culture, playing an important role in origin stories and cosmology, as well as in defining what it is to be human. In the Aboriginal story above for instance, the strange ‘hybrid’ character of the platypus reminds us to accept and learn from our differences. To early European observers, the platypus must have seemed like the ultimate foreign creature, an almost perfect embodiment of mythical animal-assemblages such as the Chimera, a fire-breathing, androgynous, composite creature of ancient Greek legend that had the head and body of a lion, a snake for a tail and the head of a goat emerging from its back. But the platypus does not merely look like an odd melding of different species; recent scientific research has revealed that the platypus also has a very complex genetic lineage. Studies on platypus venom, which is secreted from a gland in the male’s hind legs and delivered by a ‘spur’, or hollow claw-like structure, have shown that their venom contains 80 different toxins, which share genetic similarities to poisons produced by snakes, lizards, spiders, starfish and sea anenomes, as well as containing 3 proteins that are unique to the platypus. [4] Despite these genetic similarities, this research suggests that platypus venom is an example of convergent evolution, whereby similar traits in different genetic lineages can arise independently due to similar environmental pressures. The eye, wings and fins are all examples of convergent evolution. Thus it seems that whilst the platypus appears to closely resemble a range of other species – both on the surface and genetically – it is nevertheless a uniquely adapted and very special creature indeed.

Platypus taxidermy specimen at the Grant Museum of Zoology. © The Grant Museum, UCL.

Platypus taxidermy specimen at the Grant Museum of Zoology.
Photograph © The Grant Museum, UCL.

 


References:

[1] Brian K. Hall, The Paradoxical Platypus in BioScience, Vol. 49 No. 3 (March 1999), p. 211. 

[2] George Shaw, The naturalist’s miscellany – Platypus Anatinus, June 1799, Vol. 10, published by Frederick P. Nodder, (London 1813/14). Available online from the Library of NSW.

[3] Helen F. McKay, Pauline E. Jones, F. Francis & June E. Barber: Gadi Mirrabooka: Australian Aboriginal Tales from the Dreaming. Libraries Unlimited (2001), pp. 57-60 & 83-85.

[4] Ewen Callaway, Poisonous Platypuses Confirm Convergent Evolution in Nature, (October 12th 2012).

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