A Natural History of the Baleen Beasts

Evolution has taken many a curious turn through the millenia, as, a century and a half after Darwin's first work, any student of natural history probably understands. Earlier this week, Carl Zimmer explored the sequence of developments that led to the largest creatures ever on earth over at The Loom, his wonderful science blog. As he notes, these creatures didn't always have baleen; antecedent species within their sequence had teeth, and later species seem to have had both:

Some of these transitional whale fossils not only have teeth but also have marks suggesting they also held baleen. (Baleen plates are not giant teeth. They are made of keratin, the stuff in our hair and fingernails, rather than enamel.) As Fitzgerald's tree shows, the mixed-mouth whales gave rise to new species that kept the baleen and lost the teeth. They had become fully adapted to a new style of filter-feeding, and the results were dramatic: baleen whales proceeded to evolve to much bigger sizes. With the emergence of the blue whale, they became the biggest animals to ever exist on Earth.

It's a fascinating article. I'm endlessly curious about the coming into being of the present world; if that's a curiosity you share in any measure, click on over; you'll enjoy the whole article.

Thanks to Pharyngula and to NOAA for the image, a blue whale.