Arguably the most unique ability of humans is the ability to communicate highly complex concepts, for which we need language. But language can mean many things, from sign language to writing, although the most efficient form of language we have is speech – a skill unique today to living modern humans. The apes have a remarkable capacity for language and communication: Kanzi the bonobo (fig. 1) has a working knowledge of perhaps thousands of words and Koko the gorilla understands and uses American Sign Language. But they are unable to speak. Why is this? What are differences between human and ape anatomy that allow us to produce these sounds, and what selection pressures may have driven the evolution of our highly specialised anatomy?
Our species Homo sapiens has been around for some 200 000 years, and is generally thought to have evolved from older human species present in eastern and sub-Saharan Africa (University of Utah, 2005). But how did we come to be global (and even lunar) mammals? Debate still rages over how long ago H. sapiens left Africa, with some people arguing as late as 50 000 years ago and others as early as 200 000 years ago.
There is matching controversy about how we spread out of Africa: was there only one African exodus, or many spread over a longer time period? Did all or only one of them make it past the Near East? Did we completely replace older Homo species who already lived across Eurasia, or did we interbreed with them? If we did interbreed, was it complete free love that hippies would have been proud of, or did it only happen occasionally? (Reyes-Centeno et al., 2014). These questions may be a bit closer to being solved thanks to some recently unearthed fossils (fig. 1).
Wikipedia has quite an extensive piece on cranial deformation, which is a form of body modification practiced throughout history and prehistory in many cultures from all over the world, from the Pacific Islands, to South America to Europe. From a very early age, a baby’s head is bound, often between planks of wood to force the developing bones of the cranium to grow and set in a particular manner. Individuals with deformed skulls may be thought to be more
intelligence intelligent (ironic, eh?), closer to the spirit world and have a higher social status.
Some of the most famous examples of deformed crania are those of the Paracas culture which existed in the Peruvian Andes between 2100 and 2800 years ago:
Altitude sickness comes from lack of oxygen in the atmosphere, but lack of oxygen can cause other complications.
Despite this, some specific populations across the globe compensate through biochemical specialisations in the way their bodies operate. This is particularly obvious in tribes living the Andes or high up on the Tibetan plateau, some 4000m above sea level, where the air only contains 60% as much oxygen as at sea level. These adaptations are generally acquired through natural selection favouring those in the original population who, through natural variation, are built to cope slightly better than others. Over thousands of years this leads to the evolution of coping mechanisms, although the coping mechanism evolved by a population in the southern Andes may not be the same specific change as that evolved by a tribe in the northern Andes.
An example of this phenomenon can be seen in the appearance of blond hair, which evolved twice as our species, Homo sapiens, spread across the globe from around 100 000 years ago: in Europeans several modified genes contribute to producing blond hair in a person, whereas Solomon Islanders also have modifications in another gene which remains unchanged in Europeans with blond hair.
With Wimbledon in full swing and Rafael Nadal looking as fearsome as ever I’ve decided that the middle-class British sporting world and the world of physical anthropology should collide.
I’ve always thought Mr. Nadal looks a bit Neanderthal-y, and it seem as though the internet agrees with me. But would Nadal be as good at tennis if he really were a Neanderthal?
Neanderthals (Homo neanderthalensis) are known for being very strongly built and capable of producing very powerful movements of the arm. So far so good for my Nadal Neanderthal hypothesis. The problem comes when you examine the anatomy of the shoulder joint itself. Movement at the shoulder takes place between the head of the humerus (the bone of your upper arm) and the glenoid fossa which is part of the shoulder blade, or scapula (fig. 1).
The shoulder is a ball and socket joint which means that it has a really high range of motion allowing us to rotate our shoulder in all sorts of directions. In a joint, the surface area of the two bones in contact related to the range of motion at that joint, and the strength of the forces that are transmitted through this joint.
Comparing a Neanderthal and a modern human shoulder shows that the Neanderthal glenoid is taller relative to its width than is expected for a modern human. The Neanderthal glenoid is also narrower relative to the width of the humeral head than is expected for a modern human (Churchill & Trinkaus, 1990).
These differences are the same as those between Neanderthals and our ancestors, the anatomically modern Homo sapiens who were around at the same time, so it’s definitely not a case of modern humans being skinny, weak versions of Neanderthals.
Just a quick one today. I read an article earlier this week over on Live Science about the evolution of Neanderthal skull form and thought that one point in the article needed a bit of clarification.
“[…] many of the Neanderthal-like features in the Sima fossils were related to chewing. “It seems these modifications had to do with an intensive use of the frontal teeth[…] The incisors show a great wear, as if they had been used as a ‘third hand,’ typical of Neanderthals.”
Sima refers to Sima de los Huesos, or Pit of Bones, a very important fossil site in Spain where all of the Neanderthal fossils used to draw this conclusion were found.
The authors mention that one of the first behaviours to characterise Neanderthals was the use of their teeth as a tool, or a ‘third hand’ as it was put in the original article. While this is a well-accepted behaviour of Neanderthals, there has been quite a bit of debate as to how important this behaviour was in Neanderthal evolution (e.g. Rak, 1986; Spencer & Demes, 1993; Clement et al., 2012).
In the early days, it was thought that habitual strong biting at the incisors would cause rotation of the face as shown by the arrows in fig. 1 (left, top). It’s well-known that the skeleton responds to stresses and strains by laying down more bone in the most highly stressed regions. It was thought that this process could result in the more protruding faces of Neanderthals, whose triangular plate of bone below the eyes and around the nose provided strength to resist bending and rotation (Rak, 1986). This is known as the Anterior Dental Loading Hypothesis.
Very soon after, people started disagreeing with this view (e.g. Trinkaus, 1987) but the debate continues (e.g. Clement et al., 2012), with studies focusing on modern Inuit who also exhibit highly worn incisors as a result of using them for behaviours other than feeding, namely to process seal hides to prepare them for clothing.
Although Neanderthals and modern Inuit populations both exhibit comparable alterations in facial form to be able to produce stronger bites at the incisors, the degree of wearing is no different between the two. Therefore, if the effects of habitual strong biting at the incisors were responsible for Neanderthal facial form, we would expect to see similar facial shape in modern Inuit populations, which is not the case.
Based on this, the Anterior Dental Loading Hypothesis is unlikely to be true.
To re-iterate, I agree with the quotation that Neanderthals used their teeth as tools, and it also seems that this behaviour was important early on in the evolution of Neanderthals.
However, the Live Science article isn’t very careful about separating the appearance of dental wear in the fossil record from the evolution of the protruding Neanderthal facial shape.
I hope I’ve been slightly clearer.
p.s. A huge fossil-themed thank you to everyone who’s helped me reach 2000 views!
Clement, A. F., Hillson, S. W., & Aiello, L. C. (2012). Tooth wear, Neanderthal facial morphology and the anterior dental loading hypothesis. Journal of Human Evolution, 62, 367–76. doi:10.1016/j.jhevol.2011.11.014
Rak, Y. (1986). The Neanderthal: a new look at an old face. Journal of Human Evolution, 15, 151–164.
Spencer, M. A., & Demes, B. (1993). Biomechanical analysis of masticatory system configuration in Neandertals and Inuits. American Journal of Physical Anthropology, 91, 1–20. doi:10.1002/ajpa.1330910102
Trinkaus, E. (1987). The Neandertal face: evolutionary and functional perspectives on a recent hominid face. Journal of Human Evolution, 16, 429–433.
Although it may seem like we are definitely the winners in the race for survival, we can also claim to be the runners-up. Why? Because as I explained last week, humans are better adapted for efficient fast running than Neanderthals were. Now, I’m definitely not suggesting that this is the reason that we’re still here and Neanderthals died out 30 thousand years ago, but it does seem as if the ability to run quickly over very long distances may explain the shapes of our bodies now. Not to mention some people’s willingness to run marathons and Iron Man races and all sorts of other horrible things.
A true race for life
Endurance running may not just be for ‘fun’ as some people like to call it. I seem to remember watching a documentary once that spoke about Australian Aborigines running kangaroos into the ground over a distance of 50 miles, then killing them for meat. It is also possible that such persistence hunting was used by late Homo erectus and early Homo sapiens to add meat to their diet before projectile weapons were invented.
So how does persistence hunting work?