By all accounts Homo neanderthalensis should’ve driven Homo sapiens extinct. They had larger brains, stronger muscles and thicker bones. Yet we are the only species of Homo alive in the world today, creating one of the most puzzling aspects of recent human evolution. How did we beat the neanderthals?
Answering this question is made even more difficult by the fact that every time scientists believe they have found something which separates humans from neanderthals, it is promptly discovered neanderthals had that trait too.
In the past the fact we used fire (showing we were more intelligent), ate plants (showing we were more adaptable) and had personal ornamentation (showing our culture was more developed) – but neanderthals didn’t – has been used as evidence we were superior. Yet it turns out neanderthals used fire, ate plants and had personal ornamentation too.
Recent research, however, seems to have discovered a difference between Homo sapiens and Homo neanderthalensis which might explain why we out-competed them: our brains are a different shape to theirs.
On the bottom of our cranial cavity are depressions, technically called fossa (that’s your science word of the day), in which the brain sits rather snugly. Thus the shape of the brain is related to the shape of these fossae, which in turn means we can infer the shape of bits of the brain from the shape of the fossae these bits rest in.
And that is precisely what the scientists did. They compared the fossae of humans and neanderthals – specifically those fossae in which the frontal lobes, olfactory bulbs and temporal lobes sit – in an effort to determine if our brains are differently shaped to theirs.
The analysis revealed that Homo sapiens‘ olfactory bulbs were larger than those of neanderthals, who also had more oval shaped bulbs. Our frontal lobes are also wider, as are our temporal lobes which are also longer. Neanderthal temporal lobes did have an increase in width, but not as much as modern humans.
So, what does this all mean? Well,the olfactory bulbs are responsible for our sense of smell and how their size and shape influences this sense has been extensively studied. That research suggests that our bulbs would result in a better sense of smell than a neanderthal’s bulbs.
As well as giving us the advantages associated with an improved ability to sniff, a better sense of smell is also correlated with a better immune system and a better memory.
Now, that’s not to say that a better sense of smell gives one better memory but that the association of memories with odours makes those memories stronger. Nor does a larger olfactory bulb give us a better immune system. Instead, a larger olfactory bulb is typically associated with an increase in size of the other bits of the brain associated with immune response.
The other changes to the brain are less well studied, but at least now the data is there for future reference should someone identify the implications of having a wider frontal lobe etc.
There is some current use for that information, however, since they also ran this analysis on older members of Homo. This allows the frontal and temporal lobe changes to be placed in an evolutionary context. Such a placement suggests that whilst neanderthals had a larger brain, structurally it was more primitive. This might help explain why we out-competed them.
At this point I would normally go on to discuss the strengths and weaknesses of the paper, but this one appears fairly strong. The analysis is rigorous, the data used to infer we had a better sense of smell and its implications is strong and where they don’t have the data to make such inferences they don’t guess, they just say ‘there’s insufficient data.’
One shortcoming is that they didn’t use very many neanderthals in the study, which could mean the results are simply an artefact of individual variation: we didn’t have larger olfactory bulbs, the scientists just found some neanderthals with freakishly small bulbs by accident.
So some further up research may be required, but all in all its a fairly rigorous study and I fully expect its conclusions to be borne out by any replication.
As such, it seems fairly safe to conclude we did have differently shaped brains to neanderthals and this was likely a factor in allowing us to outcompete them. There were likely other factors too, but at least one piece of the puzzle is in place.
|Henry, A.G., Brooks, A.S. & Piperno, D.R., 2011. Microfossils in calculus demonstrate consumption of plants and cooked foods in Neanderthal diets (Shanidar III, Iraq; Spy I and II, Belgium). Proceedings of the National Academy of Sciences, 108(2), pp.486 -491.|
|Bastir M, Rosas A, Gunz P, Peña-Melian A, Manzi G, Harvati K, Kruszynski R, Stringer C, & Hublin JJ (2011). Evolution of the base of the brain in highly encephalized human species. Nature communications, 2 PMID: 22158443|
|Rightmire, G.P., 2004. Brain size and encephalization in early to Mid‐Pleistocene Homo. American Journal of Physical Anthropology, 124(2), pp.109-123.|
|Zilhão, J. et al., 2010. Symbolic use of marine shells and mineral pigments by Iberian Neandertals. Proceedings of the National Academy of Sciences, 107(3), pp.1023 -1028.|