A paper I recently saw in EMBO Reports made the following assertion:
Ancient Greek philosophers laid the groundwork for the scientific tradition of critical inquiry, but they nevertheless missed out on one aspect important to modern science. Many philosophers obtained their results through a tradition of contemplation and thought rather than experimental procedure, which, not surprisingly, led to errors. Aristotle?s belief that the brain is a cooling organ for the blood was definitely not based on anything that scientists today would consider scientific evidence. He also thought that in humans, goats and pigs, males have more teeth than females, a notion easy enough to correct. His statement that flies have four legs was repeated in natural history texts for more than a thousand years despite the fact that a little counting would have proven otherwise.
Say what? Aristotle was not an observer? He had no evidence for his views? That sounds wrong… and it is.
The thing about brains is often repeated because Harvey made a lot of it. But in point of fact brains do cool the blood – at least, in humans. They also do one or two other things, but we should beware simplistic functional ascriptions the way we should beware simplistic historical myths. Aristotle was not wrong so much as insufficiently right. There’s a difference.
The thing about teeth is also instructive. Robert Mayhew, in chapter 5 of his book The Female in Aristotle’s Biology, points out that observation need not have changed Aristotle’s mind. Despite there being other texts that support the equality of tooth number, Aristotle’s observations, assuming he made them, may have been on individuals who had poor diet, lacking in vitamin C, leading to tooth loss throughout their lives. Or it may have been that his theoretical commitments to teeth being instruments not only of nutrition but of defense, led to the conclusion that women do not engage in defense and thus lack the teeth needed. Either way, it was not something that could be resolved by a few simple observations.
But I want to focus on the mayfly. Here is the offending text, from History of Animals 490a?b:
All creatures that are capable of motion move with four or more points of motion; the blooded animals with four only: as, for instance, man with two hands and two feet, birds with two wings and two feet, quadrupeds and fishes severally with four feet and four fins. Creatures that have two winglets or fins, or that have none at all like serpents, move all the same with not less than four points of motion; for there are four bends in their bodies as they move, or two bends together with their fins. Bloodless and many footed animals, whether furnished with wings or feet, move with more than four points of motion; as, for instance, the dayfly (ephémeron) moves with four feet and four wings: and, I may observe in passing, this creature is exceptional not only in regard to the duration of its existence, whence it receives its name, but also because though a quadruped it has wings also.
All animals move alike, four-footed and many-footed; in other words, they all move cross-corner-wise. And animals in general have two feet in advance; the crab alone has four.
Now several things should be noted: he doesn’t say all flies have four legs; he mentions a particular animal, the “ephemeron”, which is most likely a species of mayfly, or Ephemeroptera, of which there are over 2000 species. Go look at the left hand photograph of the Hexagenia species shown here:
How many legs does it have? Well, it is standing on four, because the forelegs are specialised simply to hold onto the female during mating in flight (the sole task of the adult mayfly). Aristotle, who counts legs based on their functionality, is in fact correct, if that is the kind of species he was observing. We say it has six legs because the forelegs are homologous with the hindlegs. He said four because the forelegs aren’t used for walking.
Secondly, note that Aristotle mentions the ephemeron in the context of *walking*, where he makes the point that motion requires four points of contact with the ground, even if the animal has no legs. Moreover, it is “not less” than four. So he may be excused for not using modern concepts and criteria, but he is not guilty of misobservation, as so many want to make out. In fact, Aristotle was a damned good naturalist observer. For example, he observed and reported live birth among dogfish some 2200 years before that observation was made by modern scientists. If Aristotle wasn’t a scientist and a good observer, nobody ever has been. William Macgillivray, in 1834, wrote:
Natural history, considered as a science or body of doctrine, commenced with Aristotle, the founder of the Peripatetic School, and one of the most illustrious philosophers of antiquity. His writings were held in the highest estimation by his own countrymen the Greeks, as well as by the Romans: they were considered as the most authentic sources of knowledge, after the revival of learning in Europe; and even at the present day their influence may be traced in the works of many who have not so much as bestowed upon them a cursory glance.
Moreover, Aristotle knew that insects had six legs. In the Parts of Animals he wrote:
The anterior legs [of insects] are in some cases longer than the others, that they may serve to wipe away any foreign matter that may lodge on the insect’s eyes and obstruct its sight, which already is not very distinct owing to the eyes being made of a hard substance. Flies and bees and the like may be constantly seen thus dressing themselves with crossed forelegs. Of the other legs, the hinder are bigger than the middle pair, both to aid in running and also that the insect, when it takes flight, may spring more easily from the ground. This difference is still more marked in such insects as leap, in locusts for instance, and in the various kinds of fleas. For these first bend and then extend the legs, and, by doing so, are necessarily shot up from the ground. It is only the. hind legs of locusts, and not the front ones, that resemble the steering oars of a ship. For this requires that the joint shall be deflected inwards, and such is never the case with the anterior limbs. The whole number of legs, including those used in leaping, is six in all these insects.
Who is responsible for this long standing canard? It is worth noting that in general those of the seventeenth century tended to deprecate Aristotle (many being motivated by the neo-Platonist revival of the time) in order to enlarge their own novelty or stature. Jan Swammerdam for example consistently deprecated Aristotle’s achievements. However, I cannot find anyone who actually repeats in, on a search though archive.org. In fact in a late nineteenth century text I found someone who mentioned the mayfly, but correctly restricted it to that one organism. Moreover a search through several histories of biology, from Nordenskiöld to Magner, failed to find that canard. So I wonder if this is in fact something invented in the last 50 years or so. Anyone have any ideas?
At any rate, the more I read Aristotle, and the more I understand both where things stood at his time and what he actually said, I find him to be an amazing natural historian, a good observer, and generally not a bad theoretician. Sure, his theories are wrong, and his overall philosophy of teleology in biological cases (not, I hasten to add, in his physics) is unnecessary now we have teleosemantic explanations (i.e., natural selection), but he is not the moron of popular history of biology; far from it.
Funnily enough, the EMBOR author of the canard, Katrin Weigmann, is trying to make the case that science is not infallible, while ignoring the very real actual achievements of the people she denigrates. Nobody thought science was infallible anyway, but trying to make out that errors were made where they weren’t doesn’t give one much confidence in any subsequent argument. And of course this is another case of scientists doing bad history for [scientific] political reasons.