DNA suggests sloths, armadillos and anteaters are each other’s closest relatives

When one thinks of sloths

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anteaters

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and armadillos

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it’s difficult to imagine mammals that are more different from each other.

Sloths look a bit like lorises and pottos: arboreal, tailless mammals that move quite slowly.

Armadillos look somewhat like pangolins, with their scaly armor.

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Technically, pangolins, also known as scaly anteaters, probably have more in common with anteaters. They have strong arms and curved claws for digging up termites and ants, long tongues for eating these prey, and completely lack teeth.

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Despite their overall anatomical differences, sloths, armadillos and anteaters are more genetically similar to each other than they are to any other mammals.

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Here’s a phylogeny [1] that utilized 35,603 letters of DNA and compared 164 different species of mammals. It shows that sloths (Bradypodidae, Megalonychidae), armadillos (Dasypodidae) and anteaters (Myrmecophagidae, Cyclopedidae) come out together (yellowish-orange part of tree at the bottom) to the exclusion of other mammals. Lorises and pottos (Lorisidae) come out with primates (blue) and pangolins (Manidae) come out with carnivores (green) on completely different parts of the tree.

Not only do sloths, armadillos and anteaters have more similar DNA, but they also have a few anatomical characteristics that unite them. An important and unique one is that they possess extra articulations between their vertebrae, which has given them their official scientific group name, Xenarthra (“strange joints”).

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The evolutionary explanation for why these three very different groups of animals could be genetically similar to each other is that they share a common ancestor that lived about 65 million years ago and have since evolved very different anatomical features and lifestyles. They retain signatures of their shared evolutionary history through the retention of genetic similarity and anatomical features, such as the xenarthrous vertebrae.

Questions for Creationists

If God created all animals, including their DNA, why are animals as different as sloths, armadillos and anteaters more genetically similar to each other than they are to animals that look more physically similar to them, like lorises and pangolins? Shouldn’t DNA similarity correlate with anatomical similarity?

References

1. Meredith, R. W., Janečka, J. E., Gatesy, J., Ryder, O. A., Fisher, C. A., Teeling, E. C., … & Murphy, W. J. (2011). Impacts of the Cretaceous Terrestrial Revolution and KPg extinction on mammal diversification. Science334(6055), 521-524.

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2 thoughts on “DNA suggests sloths, armadillos and anteaters are each other’s closest relatives

  1. Pingback: Pseudogenes: Sloths and armadillos cone pseudogenes suggest subterranean history | Evolution For Skeptics

  2. Pingback: Biogeography: Xenarthrans originated and have (mostly) lived in South America | Evolution For Skeptics

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