Sunday, 12 August 2012

Evolution of the athlete

Felicity Russell

As the London 2012 Olympics draw to a close and we have watched how our athletes push their bodies to the extreme to achieve award winning performances, it is easy to see what an amazing species we are. A species more advanced compared to the many other living creatures that we share our planet with. Especially as our closest living relative happens to be the chimpanzee, that split from us 6-8 million years ago. How is it that tree dwelling apes evolved into a species capable of such athleticism? Only recently numerous fragmentary fossils have been discovered which start to reveal our origins and how we came to evolve.

The oldest suspected hominin species found is Sahelanthropus, thought to be 6-7 million years old. The skull appears ape-like but has a distinctive browridge like other identified hominin species. The hole at the base of the skull where the spinal cord passes (foramen magnum) is horizontally orientated suggesting a bipedal posture. Another indication of a hominin species is provided by the shape of its teeth, Sahelanthropus has small canines unlike the larger sharp ape-like canines. Ardipithecus ramidus and Ardipithecus kadabba, thought to have lived between 5.8-4.3 million years ago, are two more examples of hominins where tooth shape indicates a more human like function. However, clues found from Ardipithecus toe bones controversially suggests bipedalism, as joint surfaces are different in humans whose feet flex up to a greater extent than chimpanzees.

Australopithecus species, such as Australopithecus afarensisAustralopithecus anamensis and Australopithecus africanus, lived approximately 3 million years ago. They have thicker tooth enamel compared to apes and the shape of their canines and premolars suggest a more human function. The presence of shorter, broader hips is indicative of a more human like posture and leg bones have revealed human like features. The Paranthropus group, often thought as part of the Australopithecus group, existed 2.5 million years ago. They are also described as bipedal and interesting dental evidence suggests they were especially well adapted to eating nuts and seeds.

Early Homos, such as Homo habilisHomo rudolfensis and Homo erectus are thought to have lived within the last 2.5 million years, coincident with discoveries of stone tools. A bigger brain size has often been associated with early Homos, suggesting they are more like Homo sapiens (‘intelligent man’). Three new fossils have recently been discovered supporting claims that Homo rudolfensis is a separate species from Homo habilis. Later Homos include Homo heidelbergensis, Homo neanderthalensis and Homo floresiensisHomo heidelbergensis lived 300,000 to 700,000 years ago and wooden spears have been found nearby indicating that they hunted large animals. Homo neanderthalensis are thought to have used more advanced stone tools to carve meat from larger mammals. They had a large browridge and a human-sized brain. They are also known to have buried their dead and the more recent Neanderthals also made simple jewellery from animal teeth. They may have gone extinct as recent as 30,000 years ago. Homo floresiensis is the most recent distinct species, living up to just 17,000 years ago. They were short, often referred to as hobbits, and despite having smaller brains researchers have still found evidence that this species also used tools. Homo sapiens may have existed as long as 200,000 years ago originating from Africa and by 30,000 years ago they replaced Neanderthals in Europe.

Did humans evolve to run? ILLUSTRATION BY PHIL DISLEY
Noakes and Spedding (2012) have now suggested that it is our ability to run and to dissipate heat which aided our evolution. As forests disappeared and large open savannahs appeared, our ancestors had to adapt and evolve from a skeleton developed for tree climbing to a structure required for walking and even running. A lack of body hair and the ability to sweat as much as 3 litres in an hour meant we could lose heat more easily and enabled us to chase after four legged prey which require panting as a mechanism to dissipate heat. The prey would not be able to pant and run at the same time and eventually would be driven to heat stroke. The development of longer legs, shorter toes, a stronger gluteus maximus, larger weight bearing joints and broader shoulders is suggested to have aided our ability to run long distances. We have also been able to develop an aerobic capacity capable of supporting such long distance runs unlike any other ape species. Therefore as you celebrate how extraordinarily well our athletes have done for London 2012, remember how remarkable evolution can really be.

Fun point: Australopithecus anamensisAustralopithecus afarensisAustralopithecus africanus – try saying this over and over again it is definitely a tongue twister. 

The evolution of human stance

More information:

Fossil record of early humans -