Fetal whales have hindlimb buds

DNA suggests that whales are descended from hoofed mammals, and the fossil record also appears to document a transition of four-limbed whales to modern species that only have forelimbs. Looking at the ontogeny, or development, of whales also provides evidence of a past when the ancestors of these aquatic creatures walked on land. Below is a picture of an …

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Fetal sloth teeth point to evolutionary history

Sloths are strange creatures in many ways. In addition to their slow movements and suspensory way of life, they have a chambered stomach like a cow, algae species that are found on their hair and nowhere else in the world, moths whose life cycles are entirely tied to sloths ("sloth moths"), surprisingly degenerate vision, and strange …

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Legless lizard embryos have hind limb buds

As I discussed in a previous post, molecular phylogenetics suggests that many lizards evolved to become legless over time. One might wonder if there is any evidence of this legged ancestry during their development. In fact, at least some legless lizards possess limb buds as embryos. One particular example comes from the sheltopusik (Ophisaurus adopus), a legless …

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Fetal baleen whales develop with remnants of toothy past

Baleen whales include the world's largest mammals, such as humpback, bowhead and blue whales. Despite their immense size, which necessitates consuming an enormous amount of food, they completely lack teeth. Instead, they possess rows of a broom-like protein called baleen, which they use to filter clouds of tiny organisms (plankton) from the water column. Despite …

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Developmental biology: When embryos point to evolution

While scientists find evidence of evolution in fossils, DNA, broken genes, and where organisms live, few people realize that sometimes developing embryos can point to an organism's evolutionary past. This concept was popularized by scientist Ernst Haeckel (1834-1919), who suggested that humans, and other animals, would resemble different stages of their evolutionary history during development. …

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