Version: v1, Published online: 1998
Retrieved January 21, 2018, from https://www.rep.routledge.com/articles/thematic/species/v-1
The diversity of life is not seamless but comes in relatively discrete packages, species. Is that packaging real, or an artefact of our limited temporal perspective on the history of life? If all living forms are descended from one or a few ancestors, there may be no real distinction between living and ancestral forms, or between closely related living animals.
Received wisdom holds that species are the ’units of evolution’, for it is they that evolve. They are the upshot of evolutionary processes, but, if species and not just their component organisms compete with one another, they are also important agents in the evolutionary process. If so, species are real units in nature, not arbitrary segmentations of seamless variation.
The ’species problem’ has been approached from two angles. One focus has been on specific taxa of the tree of life. What would settle whether some arbitrarily chosen organism is a member of homo sapiens or canis familiaris? This is sometimes known as the ’species taxon’ problem. An alternate way of approaching diversity has been to ask what all species have in common. What do all the populations we think of as species share? This is the ’species category’ problem.
One idea is to group organisms into species by appealing to the overall similarity. This ’phenetic’ conception is in retreat. Most contemporary species definitions are relational, the animals that compose pan troglodytes are a species, not because they are all very similar (they are very like the pygmy chimps as well) but because of their relations amongst themselves and with their ancestors. The most famous relational definition is the ’biological species concept’, according to which conspecific organisms are organisms that can interbreed, however different they look.
Relational species definitions aim to define a category of theoretical and explanatory interest to evolutionary and ecological theory. Given that there are many explanatory interests, one problem in evaluating these accounts is to determine whether they are genuinely rivals.
Sterelny, Kim. Species, 1998, doi:10.4324/9780415249126-Q100-1. Routledge Encyclopedia of Philosophy, Taylor and Francis, https://www.rep.routledge.com/articles/thematic/species/v-1.
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