Image credit: Wikipedia.
Earlier this month, I wrote about the likely extinction of the Yangtze river dolphin, also called the baiji. Today’s New Scientist reported that a video shot by a Chinese man on 19 August may show a baiji, though it is difficult to tell from the quality of the footage. Even if it is a baiji, however, one animal is insufficient to repopulate a species. While it is theoretically possible to repopulate from a single breeding pair of animals, in practice, there is typically not enough genetic diversity for this to be successful. It seems likely that even if this sighting is confirmed, the animal is still “functionally” extinct, and that the inevitable “true” extinction has only been delayed by some years.
What has made this especially poignant is that I’ve been reading a book lent to me by a good friend: Last Chance to See, by Douglas Adams (the author the Hitchhiker’s Guide to the Galaxy) and Mark Carwardine. Published in 1990, the documentary is a companion to a BBC radio series highlighting endangered animal species. With his usual wit and humor, Adams narrates their journeys to find these unique creatures. I am just reading the chapter where the group is in China, searching for baijis. Sadly, their effort to draw attention to the plight of the baijis seems to have been futile; less than twenty years later the animal is already extinct or will be so shortly.
At this point, the only potential hope I see is for us to keep the baiji alive long enough (assuming the sighting was real) for us to develop the genetic technology to perpetuate the species. A different part of the book discusses the kakapo, a critically endangered flightless bird found in New Zealand. When Adams asks Don Merton of the New Zealand Department of Conservation about what he thinks the long-term prospects are, he replies:
Well, anything’s possible, and with genetic engineering, who knows. If we can keep them going during our lifespan, it’s over to the next generation with their new range of tools and techniques and science to take it from there. All we can do is perpetuate the during our lifetime and try to hand them on in as good a condition as possible to the next generation and hope like heck that they feel the same way about them as we do. (“Heartbeats in the Night”; p. 142)
It is now up to our generation to develop the science and cultivate the interest to preserve these creatures. And perhaps there is hope: the number of kakapo has apparently doubled since Adams and friends visited New Zealand; there are now eighty-six. And the book, too, lives on in a way; an interested reader maintains a blog following the status of the featured animals and others. (See his entry on the potential sighting of the baiji.)
Image credit: Wikipedia.
I was rather upset to see that the Yangtze River dolphin, also known as the baiji (Lipotes vexillifer), is thought to be likely extinct. This freshwater dolphin, which lived only in China’s Yangtze River, is probably the first cetacean (dolphin or whale) to go extinct due to human influence. Of course, humans have been responsible for wiping out species since before recorded history, but it is disturbing that we still do so. Human-induced extinctions are always regrettable events, but I admit I am especially attached to the dolphins, and I find it quite sad to lose a species of such a highly intelligent mammal.
Cetaceans, of course, evolved from land mammals around fifty million years ago. You’d have to go back only another thirty-five million years to find the last common ancestor of humans and cetaceans. That’s less than 2% of the age of the Earth (around 4.6 billion years)!
There have been several news reports of harmful effects of sonar on dolphins and whales (and other marine creatures). As Noaki Schwarz reports in LiveScience, the United States Navy may be cutting back on its use of sonar. As the Navy has decided to become more environmentally friendly, it sought the approval of the California Coastal Commission; the commission has voted to place significant restrictions on sonar use. I hope that a good compromise between military exercise and marine animal health can be found.
The Daily Mail posted an article today about an upcoming National Geographic special (I first read about it on Propjets and Writings, though it’s since appeared in several other blogs as well). Called In the Womb: Animals, it’s a follow-up to National Geographic’s previous feature on the embryonic development of humans. Using a combination of ultrasound, tiny cameras, and computer graphics, they show the development of a dog, an elephant, and a dolphin in utero.
However, as P. Z. Myers points out in Pharyngula, the images are too “pretty.” The membranes and such appear to be missing, and the uteruses look too spacious. Don’t get me wrong—I strongly support attempts to make science more appealing to the public, and sometimes one has to fill in the details—I’m a big fan of the BBC’s Walking With Dinosaurs series. I’m looking forward to seeing this (it airs on National Geographic on 10 December), but I hope they will make clear just what they could record and what they had to “fill in.”
If you’re interested in learning more, BBC and the Daily Mail both have picture galleries, and additional information and some video clips are available at the National Geographic site.
Dolphins are my favorite animals, and I’ve always been fascinated by their interesting evolutionary path. Dolphins and whales (that is, cetaceans) are mammals like we are: they breathe air, they give birth to live young, and their spines bend up and down like ours do (not side to side like those of sharks or other fish). And like us, they are descended from four-legged land mammals. It’s quite interesting to examine the sequence of changes that resulted in them more and more adapted to living in water.
Examination of a dolphin skeleton clearly reveals our closely shared ancestry. In addition to the similar spines (vertebral columns), in their flippers, dolphins have the same bones we do in our arms. Connected to the scapula (shoulder bone) is a short humerus (arm bone), then a short radius and ulna (forearm bones), followed by the tarsals (wrist bones), metatarsals (hand bones), and phalanges (finger bones)—dolphins (and whales) have five “fingers” inside their flippers. And often tiny, vestigial hind leg bones are found buried within the animal. In fact, there was a CNN article a couple weeks ago (“Could extra dolphin fins be legs?”) discussing a dolphin with a pair of caudal fins perhaps representing the ancient hind limbs:
TOKYO, Japan (AP) — Japanese researchers said Sunday that a bottlenose dolphin captured last month has an extra set of fins that could be the remains of hind legs, a discovery that may provide further evidence that ocean-dwelling mammals once lived on land.
Fossil remains show dolphins and whales were four-footed land animals about 50 million years ago and share the same common ancestor as hippos and deer. Scientists believe they later transitioned to an aquatic lifestyle and their hind limbs disappeared.
Whale and dolphin fetuses also show signs of hind protrusions but these generally disappear before birth.
If you’re interested in more about this fascinating progression, artist Carl Buell has started a series of posts on cetacean evolution at his blog Olduvai George (which I noticed courtesy of Pharyngula). He’s just posted the first in the series, with a nice commentary accompanied by his excellent illustrations. Take a look!