The long tail of the long-tailed tit (23-5-2020)

Written by: Jan Luiten van Zanden

Among the newcomers in our garden this year is a pair of long-tailed tits (staartmees), which we see regularly in the trees surrounding our garden, and which breed probably in the outer fringes of the large hedge that surrounds it. They are really funny creatures, consisting of a small dot of wool and a long tail, always cheerful hopping from one branch to another. Outside the breeding season they form groups of 8 to 18 birds, which fly from one bush to the next tree, constantly making noises to keep in touch. In particular when they move from one tree to another they produce a characteristic ‘see, see, see….’, warning their mates that they made the cross-over to the next potential source of food. And you can be sure that the mates answer with a similar ‘see, see….’. If we are going to extent our broad welfare research at some point to the animal kingdom, I am sure the staartmees will score high in the happiness index.

But it is a bit difficult to classify the bird. It has the name of a tit, and it looks very much like a tit (een mees), but it is only distantly related to the other tits, and in fact a family of its own (tits are part of the Parus family, but the long-tailed tit is a separate Aegithalos family – and evolutionary at quite some distance from the other members of the Parus family). Moreover, the Aegithalos family consists of one species, but with many European subspecies which all look a bit alike and a bit different: the Scandinavian subspecies has a white head (‘our’ long-tailed tit has a lot of blackish stripes and a black eyebrow); the British subspecies is darker than the Middle-European, the Spanish version is even darker – and one can go on like this (a few other birds – such as the wagtails – have similar regional subspecies, so it is not entirely unique). Biologists have spent a lot of time and energy discussing the underlying problem what defines a species, and when a subspecies – such as the Scandinavian with the clearly white head – should be classified as a separate species.

The underlying problem is interesting. Biologists have developed two frameworks for ordering and analysing nature. First there is the systematic classification of all species by Linnaeus, who developed a systematic structure – by giving names to families and species within families – to order nature. This was a major intellectual achievement, and it makes sense to classify knowledge in this way (if you have to survive on the African Savannah there is a point in distinguishing a lion from a hyena, and to know what the features of those species are). In the 19th century Darwin developed a theory to explain the genesis and evolution of species, which is dynamic, ‘historical’, stressing long term changes in their features in response to environmental pressures. This dynamic view of species implies that there are constantly new species developing, that subspecies emerge and perhaps disappear again, or develop – through speciation – into real, separate species (however defined). This evolutionary approach implies that there are no fixed species, and that differences between species, subspecies and local variations will be constantly changing – on the time-scale of the evolutionary process. That is, by our standards, very slow, so nature may look like a stable system of species – as our time frame is so short – but is in reality a constantly changing system of species that are evolving. So there is a tension between the static, Linnaean system to classify species, and the dynamic view of species implied by Darwin’s evolution theory. Which leads to the confusion about the classification of the long-tailed tit. This Darwinian, evolutionary view is much more influential – much more powerful as an analytical tool, an explanation – than the system offered by Linnaeus, but somehow biologists cannot do without his system.

This issue is in particular acute when it comes to the descent of man. It is almost an obsession of paleontologists to determine when (and where) Homo sapiens was born, making it necessary to define a number of features which are characteristic of the species. But as can be expected, there are many mixed and in between hominids that are difficult to exactly classify, and it is almost a matter of taste which features of the human skeleton are considered essential for being classified as Homo sapiens. Also, the birth of the new species is increasingly pushed back in time (it used to be 100,000 years ago, new finds suggest that it might be 300,000 years ago), and whereas in recent past it was assumed that East Africa was her cradle, now very different locations – and sometimes even outside Africa – are suggested.

Is there a similar dichotomy – and tension – in economics, or rather ‘political economy’? The two giants Smith – who offers a systematic analysis of the functioning of the economy – and Marx – who presents a historical, evolutionary theory of capitalism, immediately spring to mind. They clearly present two very different frameworks for analysing economic structure and change, but Smith is also dynamic (and predicts a long run stationary state) and Marx also systematic, so the contrast is not as big as in biology. What is striking is that Linnaeus’ (1707-1778) and Smith’  (1723-1790) life cycles largely overlap, as did those of Darwin (1809-1882) and Marx (1818-1883), which is interesting, but I am  not sure what it tells us. Do we in economic history feel the same kind of tension between Smith’ and Marx’ approaches, as biologists who try to combine Linnaeus and Darwin? Why were the biologists – Darwin – able to develop a theory of change, of evolution of species, which still holds, and did the social sciences not come up with something similar for society – despite of all the attempts to do so, by Marx and others?

Continue reading: Paradise Lost (25-5-2020)