The Red Notebook

BBC: Not one but ‘six giraffe species’

The world’s tallest animal, the giraffe, may actually be several species, a study has found. A report in BMC Biology uses genetic evidence to show that there may be at least six species of giraffe in Africa.

Currently giraffes are considered to represent a single species classified into multiple subspecies. The study shows geographic variation in hair coat colour is evident across the giraffe’s range in sub-Saharan Africa, suggesting reproductive isolation.

Note the inverted commas in the headline: the chaps at the BBC don’t sound too sure. It’s the age-old question as to when a sub-species becomes a species. There’s no clear-cut answer (although reproductive isolation is usually seen as an important factor). Where some cladists taxonomists see mere varieties, others see separate species. Those who make a habit of seeing the former are known as lumpers; those who see new species everywhere they look are dubbed splitters.

I had been under the impression that lumper and splitter were relatively modern labels, but not so, as this letter from the botanist Hewett Cottrell Watson to Charles Darwin shows:

The grand difficulty for naturalists or botanists of our turn of thought, is, that the use of the word “species” by technical describers is indefinite & variable. Theoretically, it is supposed to mean objects actually & essentially distinct,—so existing as productions of nature, & reproducing only their own selves or similitudes. Practically, it means only an idea of the mind, with no more real restriction in its application to objects, than have the words “genus” or “order“. Taking J. D. Hooker & Jordan as representative men for the opposite factions in botany,—’lumpers & splitters’, the former would reduce the species of Vascular plants to three score thousand, or perhaps much fewer;—while Jordan would raise them to three hundred thousand.

To his credit, Darwin’s great friend, Joseph Dalton Hooker fully acknowledged his reputation as a lumper, writing:

[George Bentham] has now completed the MSS of his British Flora, having studied every species from all parts of the world, & most of them alive in Britain, France & other parts of Europe—Well—he has turned out as great a lumper as I am! & worse

Not that there’s anything particularly wrong with being a lumper (or a splitter), you understand: it’s just a matter of tending to see things from different perspectives. And having differing perspectives is usually a good thing in science.

• Extensive population genetic structure in the giraffe (BMC Biology, 670kb PDF)
• There Are More Giraffe Species Than You Think (Living the Scientific Life)
• Now We Are Six (A Blog Around the Clock)

In science, even self-evident truths need to be put to the test. There was an interesting story in the Telegraph last week, which described how scientists have tried to show that the long necks of giraffes are adaptations to give them an advantage over shorter animals when grazing trees. Bleeding obvious, you might think, but it has also been suggested that giraffes’ long necks might be a result of sexual selection. Although the scientists concede that their experiment is not definitive, they conclude that giraffes browse at high levels in the leaf canopy out of preference (to avoid competition with shorter browsers), rather than simply because their necks happen to be long.

A small victory for common sense, then.

My first lesson in giraffe evolution occurred when I was about six years old. My primary school teacher explained to the class how giraffes tried to stretch their necks to reach the higher leaves and, over time, all giraffes ended up with longer necks. Little did I realise at the time that I was being taught a Lamarckian version of evolution. I’m sure this was not a deliberate mistake on my teacher’s behalf: she probably thought she was introducing us to Darwinian thinking.

Come to think of it, that was the only lesson I ever received in evolution at either primary or secondary school. English school biology in my day was all about the organs of species, not their origins. I wonder if it has changed much.