Genetics of South American rodents points to evolution

Rodents are an extremely successful group of mammals. There are more species of rodents than any other type of mammal, and they inhabit nearly every stretch of land on earth. Some rodents are geographically restricted, however, with a number of groups being located entirely in the Americas. Chinchillas and viscachas (Chinchillidae) are exclusively found in …

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Why Australia is the land of marsupials

Marsupials are a group of mammals generally characterized by having their young develop in a pouch, known as a marsupium. Besides this trait, there isn't anything obvious about them that screams out that they are more closely related to each other than they are to other mammals. When you place a kangaroo, Tasmanian devil, koala, marsupial …

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Why do the biggest birds all live in the southern hemisphere?

As described in my previous post, DNA and anatomy suggests that large flightless birds, such as ostriches, emus and cassowaries, evolved from a common ancestor shared with tinamous, a group of quail-like birds. These birds, known as palaeognaths, all share a relatively reptilian-like jaw, unlike most other modern birds. Other large-bodied palaeognaths are known from the fossil …

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Did 189 gecko species migrate to Australia together?

Lizards have a widespread distribution, having conquered much of the earth, but certain groups of lizards are localized to a single continent. Here I illustrate an example from geckos. Carphodactylidae includes 28 species of geckos, all of which inhabit Australia. Species include the long-necked Northern leaf-tailed gecko (Orraya occultus) and the smooth knob-tailed gecko (Nephrurus laevissimus). Then there is …

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Sloths, armadillos and anteaters have been stuck in the New World for their entire existence

Sloths, armadillos and anteaters (xenarthrans), as different as they look, are genetically more similar to each other than they are to any other mammals. This suggests that these three very different groups of animals descended from a common ancestor. If this common ancestor lived on an isolated island, we would expect that all of its …

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Whales walked in India and Pakistan before swimming around the world

The fossil record, DNA and developmental biology all suggest that aquatic whales descended from ancestors that walked on land. The geographical distribution of some putative proto-whale fossils also seems to hint at this significant transition. The proto-whale fossils that were almost completely land-dwelling, but likely spent at least some time in the water, include Indohyus …

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Biogeography: Understanding where things live and why

It may not seem intuitive, but biogeography, the study of where organisms live and why they live there, is very consistent with the theory of evolution. However, there is an abundance of uncertainty in understanding how life has spread across the globe, and it may surprise those who accept evolution to learn that in some …

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