Apologies for temporary lapse – continuing, but broadening, the swift theme.
From the evidence of fossil remains studied it seems that the modern breeds of swift have evolved from similar ancestors which survived, or benefitted from, the ‘Eocene-Oligocene extinction event’ some 30 million years ago. The history of the evolution of life-forms on Earth has been impacted by comparatively sudden episodes of mass extinctions of life-forms previously existing. The ‘Permian-Triassic extinction event’ of some 250 million years ago is thought to have killed-off some 90 per-cent of species previously existing (although the biodiversity mass would have been less than now). The ‘Cretaceous-Paleogene extinction event’ of some 66 million years ago caused the demise of dinosaur species (at the end of the Cretaceous, chalk forming, geological era).
Evolution has happened through the process of ‘speciation’ whereby varieties of organisms arise and thrive when they can adapt to a suitable ‘ecological niche’. Extinction events then must have relatively sudden happenings which intruded on the gradual progress of evolution, this inviting the question as to what caused them? Current thinking seems to be that a huge impact on the surface of the planet resulting in factors such as climate change and ecological degradation may have been responsible. A huge asteroid crashing to Earth, for example, would have had such effects.
The picture above is of a painting by Roelant Savery, a painter of the ‘Dutch Golden Age’ and from the Low Countries, who specialised in botanical and animal subjects. In particular some of his paintings show species now extinct – see, for example, the dodo grazing in the bottom-right of the picture. These he would have known of through the accounts of travellers rather than through archaeological studies of fossils.
In other words Man has caused some extinctions – a subject for next time.