A common request I get during guide training is to explain the relationship between hyrax and elephants. It seems to be one of the go-to facts when guides see a hyrax- to say “that’s the elephant’s closest living relative” or something along those lines.
In the past scientists studied animal relationships by comparing physical features. There are some features that can change very quickly, and there are features that take a long time to change, but it can be difficult to tell the difference. Scientists have to be very careful to identify features that changed more slowly over evolutionary time to determine relationships than features that change quickly over evolutionary time.
For example, both genets and cats have retractable claws, but genets are not cats. They are in the same family as civets (the Viveridae). Cats are in the cat family (the Felidae). Likewise, cheetah’s claws are different from the other cats which leads a lot of people to think that they’re not true cats, but of course they are. This is an example of a feature that can change fairly quickly- claw shape or function. This is also an example of what we call convergent evolution, where unrelated groups of animals develop a similar looking solution to an environmental challenge. (Read about the cheetah here).
If we want to understand animal relationships, we need to look at things that are deeper. Leg and foot bone structure is a fairly good one. We put zebra and horses together with the rhinos because they’re standing on the same fused toes. The horse family has just taken it to an extreme of standing on just one. There’s also fossil evidence of a three-toed horse so it makes sense that they’re closely related, and there are other features like their digestive systems that reinforce these relationships. Another good feature is to look at reproductive organs and in mammals, features like the structure of the placenta. No one doubts that the marsupials in Australia are more closely related to each other than they are to mammals outside of Australia.
Africa has a set of animals whose evolutionary history is deeply rooted called the Afrotherians. Between about 105 million years ago and less than 40 million years ago, Africa was isolated from the other continents. A “mother group” of mammals evolved on the isolated island and filled a lot of different niches from tiny insect eating elephant shrews and golden mole, to the termite eating Aardvark. One branch of that tree evolved into the elephants and hyrax and it might surprise you that sea cows or dugongs also come from this branch. Because they share an ancestry, they share some deep-rooted physical features- like placenta shape. There are some features that elephants and hyrax share. People also like to point out their jaw and skull shape, foot bone structure, and a few things like that, but the truth is that those features don’t actually make us sure. If you compare the digestive system of a hyrax with a zebra, they look and function much more alike than a hyrax stomach and an elephant stomach. The challenge is to figure out their ancestry or in other words evolutionary history. This is where advances in science really help.
We know that our DNA comes from our parents and that by comparing DNA between species and families we can get a more accurate picture of how things are related than by comparing physical features that could give us a false picture. Techniques for comparing DNA have improved and become a lot cheaper and currently the information that we’re getting from DNA studies is revealing some surprises. These techniques have also confirmed the hyrax and elephant relationship, but it is one that is very old.
Two diagrams showing the 65-70 million-year-old relationship between the hyrax family and elephant family. Scientists do not have enough evidence yet to confirm where dugongs fit into the picture but they are closely related to hyrax and elephants. Read more here.
Source: Kingdon, J et al., 2013. Mammals of Africa, Volume 1, Introductory Chapters & Afrotheria. Bloomsbury
If you want to get technical, when you’re looking at a bush hyrax (the most common hyrax) it’s actual closest relative is the tree hyrax. Their next closest relative will be a rock hyrax. The elephant we see in East Africa’s closest living relative is of course the Forest elephant of the Congo basin, and their closest relative- the Indian elephant. Some studies show that the elephants are actually also more closely related to the dugongs than they are to hyrax. Both lineages also have a lot of other closely related species that went extinct. The wooly mammoth, the fossilized elephant species found in Olduvai are all more closely related to the elephant than hyrax. Likewise, there are a lot of species of hyrax that went extinct when the hares, ruminant and rodent lineages invaded Africa.
Source article from www.safariguiding.com