Saturday, 27 March 2021
Sunday, 21 March 2021
Nonetheless, they do seem to form a distinct branch on the deer family tree - although how many species might be in that branch, and even which ones they might be, is debated. For much of the 20th century, just two or three species were recognised, but genetic evidence gathered in the 21st century has made it more obvious that some of the island forms have been isolated from their mainland relatives for long enough to become clearly distinct.
Sunday, 14 March 2021
During the Late Miocene, however, things were very different. It's hard to know the exact number of species that existed, even among the fossils we have, since some of the subtler differences may not be apparent from bones alone. But there were certainly plenty of genera, spread widely across Europe, Asia, and Africa. They were also more varied than today, and their success at the time may well have been due to the fact that actual dogs were still restricted to North America at the time, leaving the hyenas without direct competitors.
Sunday, 7 March 2021
But at least some animals do have an advantage that we don't: in addition to visual light, they can also see in ultraviolet.
In terms of physics, there's no real difference between visual light and ultraviolet; the latter simply has a higher wavelength. In a sense, as its name suggests, it's just a colour (or range of colours) that are more violet than violet. Our own inability to see it naturally gives us something of a bias here, but, in principle, there's no real reason why an animal shouldn't be able to see UV light if it would be useful to do so.