Not your average bovid; the Saiga

13 08 2007

A Mhorr Gazelle, a subspecies of Dama Gazelle, on a cold February morning at the Philadelphia Zoo

A male Gerenuk, taken in the summer of 2006 at Disney’s Animal Kingdom Park

When I think about antelope, something like a Thompson’s Gazelle, Gerenuk, or Dama Gazelle most immediately comes to mind, countless nature documentaries featuring the bovids in such numbers that they are almost easy to ignore as scenery (or as merely prey for the big cats and other carnivores). There is at least one antelope, however, that would make anyone do a double take; the Saiga (Saiga tatarica).

A Saiga, Saiga tatarica, from Wikipedia.

By all accounts the Saiga is quite distinct from its cousins on the African plains. Preferring steppe, semi-desert, and desert habitats, the Saiga is known from Eastern Europe through Mongolia, their conspicuous nose warming air coming into the body in the winter and filtering out dust during the summer. While this aspect of the Saiga’s adaptation is certainly fascinating, it is the horns of the animals that have brought it the most attention, however, as well as the most trouble. As I noted in a post about antlers, horns, and sexual selection, research has shown that males and females of bovid species (which includes antelope) that use their horns as defense against predators both have horns, the horns prevented from getting too gaudy in males because they need to retain their defensive function. In the case of the Saiga, only the males carry horns, and this allows for the horns to become relatively large, and this has greatly contributed to the decline of the species.

A male Saiga, from Sokolov, Mammalian Species, No. 38, Saiga tatarica (May 2, 1974), pp. 1-4

One of the primary problems that conservation officials face in Africa and Asia today is the poaching of animals for certain parts of their anatomy for use in Traditional Chinese Medicine (TCM), or other ritual aspects of a particular culture. To understand why the Saiga is targeted for its horns, however, we need to first look at the problems with rhinoceros poaching. Rhinoceros horns have long been treasured by various cultures, young men in Yemen traditionally carry a dagger for defense called a jambia, and there is no better material for the handle of this weapon than rhino horn. Initially, the amount of rhino horn taken was mitigated by the poverty in the region, only the most affluent families being able to afford a jambia with a handle made of genuine rhino horn. As oil prices went up, though, Yemen (among other countries) was flooded with income from the sale of fossil fuels, and the demand for rhino-horn-handled jambias skyrocketed.

Jambias are not the only reason rhinos have been slaughtered. In addition to various ornamental products, rhino horn is valuable in TCM as a fever-reducer. When actually tested it seemed to reduce fever in rats, and Saiga horn had about the same efficacy, although author Richard Ellis rightly notes in his book No Turning Back that “Asprin and ibuprofen, for which no animals have to die, would probably work just as well.” In India rhino horn was used as an aphrodisiac, but expensive prices caused practitioners to stop prescribing it. These pressures, along with others, ultimately drove the rhino population down so low that horns were rare even within illegal trade, and demand kept going up. A substitute had to be found.

The horns of the Saiga, the species only recently recovered from population declines in the early to mid-20th century, were actively endorsed by the World Wildlife Fund as a substitute for rhino horn (also see here and here. Strangely, while the WWF is one of the groups responsible for the crash of Saiga populations, they make no mention of their actions on their website, their efforts of helping the Saiga since 1994 being extolled rather than their responsibility for the near-eradication of the animals. Nevertheless, the political destabilization of Russia and other areas in which the Saiga lived made regulation near impossible, and while some researchers claim that the plains were once “blackened” with Saiga, there are probably less than 50,000 of the animals left throughout their entire range (the Mongolian Saiga, a subspecies, being reported as having a population of less than 1,300 in a 1999 paper by Lushchekina et al. in the journal Oryx).

Indeed, the tale of the Saiga is one of the greatest tales of ecological mismanagement in history, and its implications can still be felt today. Ellis, again in No Turning Back, tells us how it is unlikely that Saiga were as well-established by the time the WWF endorsed hunting Saiga as some conversationalists claim;

By the time of the Soviet Revolution, there were only a few thousand saigas left. To forestall their total eradication, the Soviets protected them in Europe in 1919 and in Soviet Central Asia in 1924. In the 1950s commercial harvests of saigas by local groups began.

Strangely, Saiga was not especially well-established in TCM until recently. Earlier texts like the 1597 text Chinese Materia Medica having no mention of the Saiga, but the 1989 Rare Chinese Materia Medica, and the ground-up horn of the male Saiga can be used to;

…check hyperactivity of the liver and relieve convulsion, treat the up-stirred liver wind, infantile convulsion and epilepsy; calm the liver and suppress hyperactivity of the liver-yang; it is efficacious in the treatment of dazzle and vertigo due to hyperactivity of the liver-yang; it improves acuity of vision, cures headache and conjuctival congestion; clears away heat and toxic material; and can be used to treat unconsciousness, delirium, and mania in the course of epidemic febrile disease.

So it does seem that the Saiga has been a more recent alternative to other traditional remedies, gaining the status of an “ancient treatment” only towards the end of the last century (although I am no expert on TCM and there could be earlier references than the ones mentioned by Ellis). As you probably have guessed by now, though, the major problem in Saiga conservation is that it is the males who are constantly targeted, much of remaining populations being females. This greatly reduces the amount of offspring that are likely to be produced, as well as marking a steep drop-off in genetic diversity and possibly even fitness in the species, the Saiga going through two near-extinctions in less than 100 years.

Male Saiga skull. Note the large shelf in front of the large nasal opening. From Sokolov, Mammalian Species, No. 38, Saiga tatarica (May 2, 1974), pp. 1-4

While the earlier near-extinction of the Saiga typically gets less attention than the more recent run on their horns, I feel that it echoes recent policies in the United States to remove wolves and other animals from protection; when stocks seem to approach levels that are barely adequate, many want to open up hunting again when the animals should actually be left alone to reestablish themselves and their genetic diversity. While some are optimistic about the recovery of Saiga, I do not share the same hope that they do. Even if raw numbers of Saiga continue to rise, I worry that the decreased genetic diversity will make them more susceptible genetic problems caused by inbreeding and disease epidemics, one “bad day” in an ecological sense being able to wipe the species out.

I would be remiss, however, if I attributed the problems of Saiga conservation entirely to hunting. As I just suggested, disease and parasites can be an important factor in terms of whether populations die off or not, something that can not be planned for by merely making sure there is more of the animals next season. In 1992, Dukes, et al. published a study that showed that paratuberculosis (or Johne’s Disease) was transmittable from domestic sheep to captive Saiga and back again. Even more recently (Morgan et al, 2005) it has been found that Saiga pick up many of the parasitic worms that also infect grazing livestock along their range, both suffering from the parasites and also allowing them to spread further. Global climate change may also adversely affect the Saiga, the Saiga depending on local climatic cues to dictate their migrations. Heavier snowfall/harsher drought may cause them to have to move to new habitats or be decimated, and at present it is unknown whether they’d be able to cope with ecological changes associated with the current warming trend.

In all, things are not looking too good for the Saiga. While there has been a ban on the trade of products made from them and conservation agencies are trying hard to preserve this species, I believe that it not exists in a weakened state, which (despite population size) will make it more susceptible to extinction. Given enough time the species may recover fully, but in my own view this has “heath hen” written all over it, a species that seemed to recover until disease, predation, and weather changes were too much for the remaining birds in New England to handle. I am not suggesting that we say the Saiga is a lost cause; far from it. What I am recommending is that we actually learn something from the terribly mistakes we’ve made with this species, and stop thinking that merely because populations increase it somehow equals immediate species stability.

Taking in the Carboniferous Atmosphere

3 08 2007

In many a time-travel story, little attention is paid to the local ecology of the destination of the intrepid travelers. If you’re headed back to visit Leonardo da Vinci, this probably isn’t going to be a problem, but if you’re headed back much further, like the Carboniferous or Permian, you might run into some trouble. Indeed, nothing could kill such a “time safari” quicker (like the one in L. Sprauge de Camp’s “Crocamander Quest,” collected in The Ultimate Dinosaur) than stepping out of the time portal/capsule and not being able to breathe. Fanciful notions of time travel aside, we can tell something about the ancient atmosphere without having to actually step foot there, and it has some very interesting implications for evolution and ecology.

One of the defining features of the Carboniferous is that things got big. Even though they may have seemed small compared to titanosaurs or mammoths, a 3-foot-long millipede and giant dragonflies are nothing to belittle. Indeed, terrestrial arthropods in all sorts of groups seemed to achieve sizes unheard of today. Why should the Carboniferous be dominated by giant arthropods?

Well, let’s think about the name of the time period we’re talking about: Carboniferous. Carboniferous deposits, sandwiched between the Devonian and Permian, are well-known for containing coal. The coal was originally laid down by the thick plant growth that marked changes in terrestrial ecology, and although the first plants (likely resembling liverworts) colonized the land as early as the Ordovician, the Carboniferous marked the development of lignified bark (“brown coal” is called lignite), which may have led to the huge amounts of coal deposited as bacteria needed some time to evolve a way to break down this new material. Due to Devonian drops in sea level, plants were also had more space to grow, so there was a greater number of swamps and forests produced, filling up with plant and insect life. The changes in global fauna had a major impact on the atmosphere, not only producing more oxygen due to photosynthesis, but the burial of so much biologically produced carbon also increased the amount of oxygen in the atmosphere, perhaps being as high as 35%! (It’s at about 21% today)

Another important piece of the puzzle is that nitrogren levels did not drop, and so not only was there hyperoxic conditions due to plant evolution, but the air pressure was increased as well, and these two factors probably had a lot to do with the evolution of insects flight and insect gigantism. When there is more oxygen in the air, organisms that diffuse oxygen over their trachea are able to obtain more oxygen with less effort, and it doesn’t take as much energy to become large being oxygen is so “cheap.” Likewise, increased air pressure makes flying less costly in terms of energy, as wing size has to go up with decreasing air pressure in order to keep flying animals aloft (as is that case with hummingbirds that live at high altitudes). Not only was it easier to grow large, but it didn’t take as much energy to fly, resulting in the giant dragonflies like Meganeura. In a 1998 paper, Dudley hypothesized that early tetrapods would have taken advantage of the extra oxygen as well, being that they would have “breathed” through their skin. This hypothesis is largely refuted, however, (see the comment of johannes below) and size of early tetrapods does not seem as dependent on the atmospheric oxygen make up, although it likely could have made oxygen intake for amphibious tetrapods more efficient overall.

There are costs to be adapted to an atmosphere with high oxygen content and high atmospheric pressure, however. Part of the cost is the buildup of metabolic “wastes” as a result of taking in so much oxygen, and unless there’s also an increase in enzymes to take care of these wastes, organisms may have led shorter lives. Experiments in the lab with fruit flies, however, have shown that an increase in enzyme production to combat the harmful metabolic products can be selected, and it’s reasonable to think that Carboniferous organisms underwent such selection naturally. Still, atmospheric oxygen levels began to sharply drop at the beginning of the Permian, and by the beginning of the Triassic atmospheric oxygen levels were as low as 15%. Creatures adapted to higher oxygen content and pressure would need to be adapted quickly again if they were to survive, and size/ability to deal with lower oxygen levels probably made a big difference in the great Permian extinction.

Oxygen levels were not always to remain low, however, and it has been hypothesized that hyperoxic conditions (which means more oxygen in the air plus heightened pressure) might be correlated with the evolution of flight, or at least evolution of larger flying organisms. When it’s less expensive to obtain oxygen and less expensive to fly, it would be much easier to develop flight, and there may be correlations with such atmospheric conditions and the evolution of bats, birds, and pterosaurs. Testing still needs to be done (and the more fossils we can get, the better), but if nothing else, the fluctuations in atmospheric oxygen content show us the importance of considering ecology in terms of evolution and extinction.


AERIAL LOCOMOTOR PERFORMANCE.” The Journal of Experimental Biology 201, 1043–1050 (1998)

Arctic ponds are drying up (I’ll give you one guess why…)

17 07 2007

Earlier this month, the paper “Crossing the final ecological threshold in high Arctic ponds” was released via the PNAS website. While public considerations of global climate change usually extend to hurricanes, polar bears, and melting glaciers, there are many more subtle signs of change that are often overlooked, although they are no less important to our understanding of how we’re changing out planet. In the paper, researchers John P. Smol and Marianne S. V. Douglas describe how over the course of 24 years, shallow ponds that have existed for thousands of years in the arctic are now found to be entirely dried up and dessicated in the summer months, the culprit almost certainly being warming in the region. While the drying of arctic ponds may not seem to be of concern to your average suburbanite, these ponds are vital for invertebrate life and waterfowl, and the absence of the ponds is going to have some dire effects of waterfowl, invertebrates, and other life that depends on them. In less than 1/4 of a century, ponds that have existed for ages disappear, in a geological blink of an eye, showing us that nature will not wait for us humans to make up our minds about what to do to curb climate change.

Extinction is apparently all the rage…

13 07 2007

One of the topics that drew me in to the study of evolution was, oddly enough, extinction. While this might seem to be counter-intuitive, evolution being the origins of species and extinction being their end, if we cannot understand or recognize extinction we’re going to have a pretty poor idea of evolution (in fact, the establishment of extinction of fact was one of the key antecedents to the establishment of evolution as fact by Charles Darwin). Despite the important of understanding how extinction happens, it’s a matter that doesn’t seem to get as much attention as it probably should, and I’ve decided to summarize a few recent papers/articles on the subject here for anyone interested in the “life and death” of species.

[Note: By “‘life and death’ of species” I do not mean the antiquated and incorrect belief that species go through stages of birth, growth, and death just like an individual organism does, owing it’s premise to a vitalistic approach to evolution. If you want to read a good refutation of such ideas, see G.G. Simpson’s The Meaning of Evolution.]

First up, a recent Nature article by Nick Lane dubbed “Reading the Book of Death,” that focuses on the Permian extinction event. While the late-Cretaceous extinction that wiped out the non-avian dinosaurs is more widely known (thanks in part to the controversy about an impact at the K/T boundary during the 1980’s and 1990’s), the end-Permian extinction was much more severe, and Michael Benton aptly called his book on the subject When Life Nearly Died (although Peter Ward is perhaps a better known “spokesman” for the Permian, especially because of books like Rivers in Time and Gorgon). . While I have yet to read Benton’s book, I am familiar with Ward’s work and the general global-warming hypothesis that was brought to life in the BBC documentary Walking With Monsters (and, in fact, Ward has a new book out that I assume attempts to tie the Permian to the present in terms of climate change, Under a Green Sky); due to volcanism or other changes, massive amounts of carbon dioxide were dumped into the atmosphere, the temperature rising by about 43 degrees Fahrenheit. Such changes, if they occurred quickly, would have dire implications for life on earth.

There is certainly more to the story, however; volcanoes don’t simply spew out CO2 and little else, and the sheer amount of volcanic activity would have had potentially larger implications than a rise in temperature. While the volcanic activity in the Siberian Traps at the end of the Permian is well known, just exactly what effects they had is still being debated. We know that there was massive amounts of volcanic activity, we know the temperature shot up, we know that a large amount of volcanism can put chemicals into the air that damage the ozone layer (hence letting more UV radiation in), that oxygen levels likely fell at a gradual rate between the Carboniferous and the end-Permian (from 30-13% oxygen in the atmosphere, the article states), and that there were carbon spikes (probably from released methane) prior to the Permian extinctions. How do all these factors come together to explain which groups survived and which did not?

Lane sums up the situation at the end Permian as a hellish nightmare of a world gone awry, the pressures on organisms at that time being so great that many would not survive;

So with dangerously low atmospheric oxygen levels, ecosystems were compressed and fragmented. The deep oceans were largely uninhabitable. Land plants were dying back in the arid greenhouse climate, making food hard to come by. And then came the hammer blows of fate, the greatest volcanic outpourings in the history of our planet, releasing vast quantities of methane and carbon dioxide, raising global temperatures by 6 °C, and lifting the Strangelove conditions to the very surface.

Head for the hills and there’s no oxygen; stay on the shores and you risk breathing hydrogen sulphide. High carbon dioxide levels sabotage your respiratory pigments and choke you from within. Even if death doesn’t get you right away, you’re unlikely to have much spare energy for sex. Population sizes fall; so do body sizes. Even for those that survive the immediate toxicity, slow extinction was likely over a few generations — the blink of an eye in geological terms.

While the importance of each of these factors may vary globally or locally, it is important to realize that extinction events are ecological catastrophes; if we try to find just one smoking gun we’ll likely be mistaken. In fact, extinction is more life a firing squad than a single bullet that knocks the whole system off-kilter. Likewise, Lane also correctly notes that the creatures that survived largely did not do so because they were able to react more quickly to a changing world. Instead, they were already pre-adapted, the precursors of dinosaurs and mammals (and even later lines that would go extinct in the Triassic) having unique systems of air-sacs, palates, or turbinate nasal bones (see the opening of Schmidt-Neilsen’s How Animals Work) that may have helped them cope with an arid world in which water was the most precious commodity of all. While the mystery of the end-Permian catastrophe is still far-from-solved, the more integrated approach of scientists working on the problem may give us a more accurate look at why some groups died while some continued to great success in later periods.

Extinction is not something that has only occurred in the past, however; it is still occurring today. In a new PLoS Biology paper “Projected Impacts of Climate and Land-Use Change on the Global Diversity of Birds,” Jetz, Wilcove, and Dobson determine that global climate change in high latitudes and destruction (and restriction) of habitat in tropical regions will probably significantly reduce a number of bird species. Part of the modern extinction problem, as outline in David Raup’s book Extinction: Bad Genes or Bad Luck?, narrowing the range of a species can set them up for extinction, even when they seem to be doing well or even recovering. The classic case study is of heath hens in New England, where despite the fact that the population was recovering, the species died out in the blink of an eye because enough adverse factors accumulated to wipe all the birds out almost overnight (see an earlier post here).

Indeed, small geographic range or isolation are strongly correlated with extinction, both past and present. Even amongst animals that are not highly specialized, the inability to spread beyond a small area makes them much more vulnerable to extinction if they cannot withstand local pressures. Conversely, wide geographic range can be a good indicator of survivorship amongst species, and this was recently detailed amongst benthic marine invertebrates by Payne and Finnegan in their paper “The effect of geographic range on extinction risk during background and mass extinction” published in PNAS. The findings of the researchers make sense; widely distributed genera fare much better in the long run than those that have more narrow environmental needs that keep them from spreading. This spread also can help spur evolution (given that ecologies are constantly changing, to a greater or lesser degree), and so a greater diversity can arise from genera that can be found over a wider range for a longer amount of time. This does not exempt such groups from extinction, the researchers warn, as more catastrophic events that effect ecology on a global scale can wipe out groups that are widely distributed just as they can specialists. Hence, wide ranges for a group is important for survivorship during times of relatively slow global ecological change, but this does not necessarily exempt then from devastating extinction events like those seen during the end-Permian (as mentioned above).

In any case, I would highly recommend that anyone interested in extinction or evolution check out the above papers and articles, as the constant overturn of life is something vital to our understanding of the history of life on this planet. In case you’re in the mood for some further reading, check out Jeremy Bruno’s post on how mass extinctions affected chelicerates, or check out any of the books mentioned above.

The Natural Selection of Coral Reefs

3 07 2007

Hurricanes are among the most devastating of weather events, and coral reefs are often damaged when in the path of a hurricane. It is quite surprising, then, to consider the possibility that hurricanes might actually be helping some coral communities reverse the “great bleaching” that has been destroying so many reefs. While it’s easy to think of corals are a primarily warm-water creature, they are actually quite sensitive to water temperature, and increased ocean temperatures (caused by the current warming trend) has caused the algae that live inside coral and are vital to the existence of coral to either die or be expelled, the coral then taking on a stark white appearance (hence, “bleached”). A new PNAS paper by Manzello, et al. suggests that the local cooling trend that follows hurricanes may benefit some reefs, however, thus giving us a look at a very strange selection process.

What the researchers found when looking at the intensity of coral bleaching at several sites in Florida and the occurrance of tropical storms and hurricanes was a suggestive correlation; as the storms passed within 400 km of the reefs, the high winds cooled water temperature, making it much easier for the reefs to rebound from bleaching. Sites that did not experience such cooling effects (high water temperatures plus no relief until the winter) had as much as 90% of the coral bleached with no notable recovery until a seasonal drop in temperature. The storms can damage the reefs however, and it seems that the reefs have to be close enough to receive the benefits of the cooled water, but not too close to actually be damaged by the storm, and the number of given storms in a year (as well as the path they take) will help to determine what reefs will be favored over others. If there is indeed a real correlation between warming sea temperatures and the occurrence of hurricanes (I suppose I should read Storm World and then talk it over with a prestigious meteorologist friend of mine), then coral reefs around Florida and other southern states may be able to recover despite the overall warming trend. This is certainly an area of research to keep our eyes on if we are concerned about coral conservation, and if the frequency of storms happens enough, it would be interesting if there was a “storm-resistant” variety of reef (keep in mind that a reef is not made up of just one species) that was selected for in this odd fashion.


29 06 2007

I always get a little bit antsy when I see morning news reports about a new study appearing in Nature, Science, or some other journal, not having access to the actual paper until sometime later in the day. This past week, however, the mass-media slipped up a bit in this regard; they announced a new paper in the Proceedings of the National Academy of Sciences about two huge, extinct penguins on Tuesday, but the paper itself has only just now become available.

Giant Penguins
Art by Kristin Lamm. From right to left; Icadyptes salasi, Spheniscus humbolti (extant Humbolt Penguin), and Perudyptes devriesi

The reason this particular paper is so significant (other than 5-foot-tall penguins being utterly cool in and of itself) is that the prevailing hypothesis for penguin evolution was that they originated in cooler, southern latitudes and eventually made their way up to warmer areas like Peru, the Galapagos, etc. after temperatures during the Cenozoic began to cool. In fact, the Eocene (the time period in which the two new penguin species pictured above lived) experienced a temperature spike that threw various systems out of whack and contributed to the extinction of many groups of animals, including mammals. At the onset of the Eocene, there was a sharp thermal spike known as the Paleocene-Eocene Thermal Maximum, following by an overall rise in temperature before cooling down, and looking at the overall trend the world was much warmer during the time of the giant penguins than it is now, reversing the notion that penguins could only advance as far north towards the equator as cold temperatures would allow.

Analysis of the two penguins (there are also species yet to be identified from the same site, so expect more from Peru in the future) shows that they are not the ancestors of living penguins, belonging to the Order Sphenisciformes but outside the Family Spheniscidae, the authors citing the radiation that produced living groups taking places approximately eight million years ago during the Miocene. While much of the mass-media has focused on the “giant” size of Icadyptes, it should be noted that Icadyptes is only one of many known large, extinct penguin varieties, the largest yet known being Anthropornis nordenskjoeldi from Seymour Island and New Zealand, other examples being Pachydyptes ponderosus and Palaeeudyptes klekowskii.

Icadyptes is notable amongst its nearly equally-sized relatives for another reason; we wouldn’t expect to find such a large penguin in such a warm climate. While a foraminiferan indicative of warm-water has been found in association with the giant Pachydyptes, it was generally assumed that penguins followed “Bergmann’s Rule.” Bergmann’s Rule essentially states that among warm-blooded animals, we should expect body mass to increase with increasing latitude (hence, colder climates). This rule seems to work not only across species, but within species as well, working on the inherent plasticity of the animals to vary their size (i.e. wide-ranging animals are usually larger in the far north or south than close to the equator). Icadyptes gives “the flipper” to Bergmann’s Rule, being a warm-blooded bird in a hot environment of equal size to contemporaries from cooler latitudes, but there are exceptions to every rule.

The general reason why we observe Bergmann’s Rule is because of body heat; if you live in the cold you want to retain it, which large body size allows you to do, and in hot climates you don’t want to overheat, so it behooves you to be small and thus give off plenty of heat. Bob Bakker provides perhaps the best illustration of this in The Dinosaur Heresies; if you have to spend the night in a zoo and want to stay warm, should you snuggled up to one elephant (and remember, elephants are large and do live in hot climates, also “in violation” of the Bergmann’s Rule) or cover yourself with 100 bunny rabbits? The rabbits, although not even coming close to the mass of the elephant, radiate more heat, and while I think 100 is a bit excessive (I don’t want to toast in my sleep), you’ll be far warmer under their mass of fur than up against the wrinkly skin of an elephant. It is therefore apparent that something else is at work with Icadyptes; either there were patterns of upwelling that kept things cool enough for them (as in the case with Galapagos penguins today), or they were somehow otherwise adapted to keep their large body size without overheating in the equatorial region.

Overall, I am probably more excited about this find than I was about Gigantoraptor, and I actually enjoyed reading the PNAS paper (you need to be up on your anatomy to get the most out of the species descriptions, but otherwise it was easily accessible), and it seems to be a rare joy to find a paper that is both important and able to keep me engaged. I can’t wait to see what else has come out of the strata in Peru, and hopefully there can be a greater collaboration between paleoclimatologists, paleontologists, ecologists, and others to find out why there were giant penguins in the very last place we would expect to find them.

Mammoths & Meteors

12 06 2007

If you haven’t done so already, check out John McKay’s excellent piece on hypotheses surrounding mammoth extinction (from “They didn’t go extinct, stupid!” to the current news of a possible comet/meteor impact 13,000 years ago), including an overview of how pre-existing thoughts and biases shaped the way we view the coming and going of different groups of animals through time. And if that isn’t enough to sate your need to learn about mammoths, John also has a post on some recent genetic studies relating to the disappearance of the big mammals, too.