Northwards and upwards

Another example of Darwin's being well ahead of the game:

BBC: British species migrate northward

Right across Britain, animals are on the march, moving northwards and going to higher ground as the climate warms, experts have told a major conference…

Chris Thomas from the University of York said the changes fitted neatly with the predictions of climate models. "Species are moving north, they're climbing mountains, they're retreating at their southern boundaries," the professor added.

Compare the above with the situation at the end of a former glacial period, as envisaged by Charles Darwin in chapter 11 of Origin of Species:

As the warmth returned, the arctic forms would retreat northward, closely followed up in their retreat by the productions of the more temperate regions. And as the snow melted from the bases of the mountains, the arctic forms would seize on the cleared and thawed ground, always ascending higher and higher, as the warmth increased, whilst their brethren were pursuing their northern journey. Hence, when the warmth had fully returned, the same arctic species, which had lately lived in a body together on the lowlands of the Old and New Worlds, would be left isolated on distant mountain-summits (having been exterminated on all lesser heights) and in the arctic regions of both hemispheres.

True, unlike in Darwin's scenario, we aren't emerging from an ice age, but the principle is the same: our climate is getting warmer and species are on the move. Exactly as Darwin predicted.

Wonderful find

Another so-called missing link rises from the dust:

BBC: 'Lucy's baby' found in Ethiopia

The 3.3-million-year-old fossilised remains of a human-like child have been unearthed in Ethiopia's Dikika region.

The female Australopithecus afarensis bones are from the same species as an adult skeleton found in 1974 which was nicknamed "Lucy".

Channel crossings

Darwin would have loved this:

BBC: Channel's key role in pre-history

A study of prehistoric animals has revealed the crucial role of the English Channel in shaping the course of Britain's natural history. The Channel acted as a filter, letting some animals in from mainland Europe, but not others.

Even at times of low sea level, when Britain was not an island, the Channel posed a major barrier to colonisation. This was because a massive river system flowed along its bed…

"We find we're getting only a selection of the mammals during the British interglacials that there are in mainland Europe," said Professor Stringer [of London's Natural History Museum]. "For example, at one pre-historic site, researchers found hippopotamus and fallow deer; but unlike mainland Europe at the time, there were no horses and no humans. This suggests that the Channel, or the Channel river system, is acting as a filter to prevent the movement of some of these [mammal] forms into Britain."

Colonisation of islands was a subject of great importance to Darwin. He devoted chapters 11 and 12 of Origin of Species to the geographical distribution of species, and islands figured heavily in his theories of speciation. He was mainly interested in mid-ocean islands, such as the Galapagos Islands, but he was always on the lookout for examples of how species could become isolated from parent stock.

Crane fly season

Crane fly
A crane fly on my window last week

It's crane fly season here in West Yorkshire. Last week, we were suddenly inundated with them. One week there wasn't any sign of them, the next they were all over the place—particularly in the evenings.

I didn't know, until I looked it up, that crane flies spend most of their lives underground in their larval forms, which are known a leatherjackets. I knew that leatherjackets were very common round here, and are a favourite food of the local crows (particularly the rooks), but I did not know that leatherjackets transform into crane flies. You learn something every day.

I naturally supposed that crane flies emerge en masse to increase their chances of encountering a mate—which I still guess is right. But then I had another thought: emerging en masse will also give the individual crane flies a better chance of avoiding being eaten by predators: plenty more fish in the sea, so to speak. And then it occurred to me that they emerge in early September, which is about the time that swallows traditionally start heading south for the winter. Could the timing of the crane flies' emergence in September be an adaptation to avoid being eaten by swallows?

If so, it isn't a 100% reliable strategy. One evening last week, a family of swallows spent a good half-hour hunting around the west-facing eaves of my house. I initially mistook them for local bats—I had not seen swallows that close to the house before. I wonder if they were hunting crane flies, which appear to be attracted to the residual warmth of the building after sunset.