Devonian Comura trilobite from Hamar Laghdad Formation, Erfoud, Morocco

The advertising description reads:

This INVESTMENT GRADE spiny Comura trilobite represents the finest possible quality of preservation, completeness and displays an entire array of authentic spines freed completely from their matrix and exposed. This species is one of the most complex and difficult to prepare in this manner and such a project encompasses untold hours of meticulous preparation and skill. All three rows of spines running down the lobes of this trilobite and all other cephalonic spines have been exposed and are 100% AUTHENTIC. The trilobite is prepared with the head (cephalon) protruding up off of the rock and rock is removed from beneath. This time-consuming fantastic, natural position gives the impression as if it is attempting to crawl off its original limestone matrix. Examples like this come along only on very rare occasion and 100% authentic examples are becoming increasingly difficult to find. Perfect for the most demanding advanced collector striving to acquire specimens based on the finest rarity and quality.

I didn’t actually realize that trilobites came in investment grade, and I bet they didn’t either, but I will gladly concede that is is one heck of a nice trilobite.

The photos don’t really make it clear that this bad boy is only 2.4” long, and the whole shooting match, rock and all, is less than 3 1/2” long. Nonetheless, they are asking $4250.

Hat tip to Fred Lapides.

A leading causal candidate for the human genetic bottleneck is the volcanic supereruption that formed Lake Toba in Sumatra, Indonesia.

Sam Kean, in Slate, explains that the number of human chromosomes suggests that modern humanity emerged from a small, inbred population.

Humans have 46 chromosomes. Our closest primate relatives have 48. So where did those extra two disappear to? ...

Let’s go back a million years, when most proto-humans had 48 chromosomes, and follow a hypothetical Guy who has 47. Again, a chromosome fused at the tips won’t affect Guy’s day-to-day health. But having an odd number of chromosomes will cripple the viability of his sperm. (If you prefer to think of a female, the same is true of her eggs.)

Say the fusion left Guy with a normal chromosome 12, a normal 13, and a 12-13 hybrid in each cell. During sperm production his body has to divide those three chromosomes into two cells, and there are only a few possible ways to divvy them. There’s {12} & {13, 12-13}, or {13} & {12, 12-13}, or {12, 13} & {12-13}. The first four sperms are either missing a chromosome or have a duplicate, practically a cyanide capsule for an embryo. The last two cases have the proper amount of DNA for a normal child. But only in the sixth case does Guy pass the fusion on. Overall, then, two-thirds of Guy’s children die in the womb, and just one-sixth inherit the fusion. And any Junior with the fusion would then face the same terrible odds trying to reproduce. Not a good recipe for spreading the fusion—and again, that’s still only 47 chromosomes, not 46.

What Guy needs is a Doll with the same two fused chromosomes. Now, the odds of two people with the same fusion meeting might seem infinitesimal. And they would be—except in inbred families, where the chances of finding a cousin or half-sibling with the same fusion don’t round down to zero so easily. What’s more, while the odds of Guy and Doll having a healthy child remain low, every 36th spin of the genetic roulette wheel (because 1/6×1/6 = 1/36), the child would inherit both fused chromosomes—giving him 46 total.

And here’s the payoff: Junior and his 46 chromosomes would likely have an easier time having children than his 47-chromosomed parents. Remember that the fusion itself doesn’t ruin you—lots of healthy people have fusions. It’s only reproduction that gets tricky, since fusions can lead to an excess or deficit of DNA in embryos. But because he has an even number of chromosomes, little Junior wouldn’t have any unbalanced sperm cells: Each would have the right amount of DNA to run a human, just packaged differently. As a result, all of his children have a good chance of being healthy. And if his children start having their own children—especially with other relatives with 46 or 47 chromosomes—the fusion could start to spread. ...

How did having 46 chromosomes then spread worldwide? It’s possible that having two fewer chromosomes than everyone else gave Guy and Doll’s family a whopping evolutionary advantage, allowing them to out-compete the 48-chromosome sluggards. But probably not. More likely, they happened to be living at a point when the human race nearly got wiped out.

Take your pick for the cause of our near-extinction—ice ages, plagues, Indonesian gigavolcanoes. But humans have far less genetic diversity than most other species, and the most reasonable explanation for this is a genetic bottleneck: a severe reduction in the population of humans in the past, perhaps multiple times. One study suggested that our population, worldwide, might have dropped as low as 40 adults. (The world record for fitting people in a phone booth is 25.) That’s an outlandishly pessimistic guess even among disaster scientists, but it’s common to find estimates of a few thousand adults, below what some minor league baseball teams draw.

Read the whole thing.

Since arriving in Virginia, Karen and I have frequently marveled at the Osage orange, a fruit-producing tree not encountered in my native Pennsylvania or in New England where we attended college and resided for decades.

The Osage orange was evidently ill-advisedly imported into Virginia as a decorative tree, and it responds to that hospitality by covering the ground every Fall with enormous bumpy fruits that nothing eats and which simply lie on the ground and rot.

I wondered out loud recently why a tree would bother to produce enormous fruits in great quantity that were inedible. Fruit production, after all, constitutes a system of bribery by members of the botanical kingdom. The tree or bush produces a tasty fruit or berry, and birds and animals consume them and consequently carry away and redistribute the plant’s seeds.

There are all those Osage orange trees busily producing gigantic, but inedible, citrus fruits that nobody wants. Why is this? I wondered. It just seemed very strange.

Happily, Karen found the answer just a few days later, in American Forests.

It turns out the Osage orange fruits, like certain others, used to have customers who liked eating them. Unfortunately, their natural Pleistocene megafauna audience went extinct.

[L]et’s return to the forlorn fruit of the Osage orange. Nothing today eats it. Once it drops from the tree, all of them on a given tree practically in unison, the only way it moves is to roll downhill or float in flood waters. Why would you evolve such an over-engineered, energetically expensive fruit if gravity and water are your only dispersers, and you like to grow on higher ground? You wouldn’t. Unless you expected it to be eaten by mammoths or ground-sloths.

According to my field guide, Osage-orange has a limited natural range in the Red River region of east-central Texas, southeastern Oklahoma, and adjacent Arkansas. Indians used to travel hundreds of miles for the wood, prized as the finest for making bows. Then European settlers planted it widely as living fences, taking advantage of the tree’s ability to spread via shoots from lateral roots. But Osage-orange persisted, and became widely naturalized long after the invention of barbed wire rendered them useless to farmers. The tree can now be found in 39 states and Ontario. If Osage-orange does so well elsewhere, why was it restricted to such a small area?

The answer likely lies in the disappearance of its primary disperser. Without mammoths, groundsloths, and other megafauna to transport its seeds uphill, the range of the species gradually shrank to the Red River region. In fact, fossils tell us that Osage-orange was much more widespread and diverse before the megafaunal extinctions. Back then, Osage-oranges could be found north up to Ontario, and there were seven, not just one, species in the Osage-orange genus, Maclura.

Another anachronistic tree is the Kentucky coffeetree, so named because early Kentucky settlers used its beans as a coffee substitute. Coffeetrees have tough, leathery pods with large, toxic seeds surrounded by a sweet pulp. Water cannot penetrate the thick seed coat to begin germination unless it is abraded or cut. Sounds like mammoth food to me. The natural range of coffeetrees is concentrated in the Midwest, but without its megafauna disperser, it is generally rare and mostly limited to floodplains.

Much the same can be said about the honeylocust, with its sweet seedpods up to 18 inches long. It is more common than coffeetrees, and is found in upland areas because cattle have filled in for the mastodons, camels, or some other dearly departed megamammal with a sweet tooth. The big-fruited pawpaws, persimmons, desert gourds, and wild squash may also have been dispersed more efficiently by recently extinct mammals.

Now when you see an Osage-orange, coffeetree, or honeylocust, you might sense the ghosts of megafauna munching on treats made just for them.

A scientific swindler preyed on American scientists working in Geology during a period extending from 1884 to 1891, obtaining books, specimens, and money from a number of American scholars. He had a good knowledge of Eastern European languages, was well acquainted with the field and frequently assumed the names of prominent authorities. By the time he vanished from history, he had also accurately identified large numbers of specimens in American museum collections.

Limestone quarried in Italy and cut into slabs intended to be used for kitchen counters was found to have accidentally produced a perfect cross section of a 40 million year old Eocene fossilized whale.

National Geographic 6:31 video

Hat tip to Karen L. Myers.

Science News:

Results show modern humans, Neandertals diverged 660,000 years ago

An international consortium of researchers reports in the Aug. 8 Cell that for the first time the complete sequence of mitochondrial DNA from a Neandertal has been deciphered. Comparison of the Neandertal sequence with mitochondrial sequences from modern humans confirms that the two groups belong to different branches of humankind’s family tree, diverging 660,000 years ago.

That date is not statistically different from previous estimates of the split between humans and Neandertals, says Erik Trinkaus, a paleoanthropologist at Washington University in St. Louis. The sequence also doesn’t reveal what happened to drive Neandertals to extinction, but it does clear up some discrepancies in earlier studies. ...

At 16,565 bases long, the new sequence is the largest stretch of Neandertal DNA ever examined. The DNA was isolated from a 38,000-year-old bone found in a cave in Croatia.

“It’s a nice accomplishment and the next important step toward completing the Neandertal genome,” says Stephan Schuster of Pennsylvania State University in University Park. Schuster is part of a group that is sequencing the genomes of the mammoth and other extinct animals, but was not involved in the current study. “It’s a nice landmark on the way to saying what makes modern humans so special.”

In order to know exactly how modern humans and Neandertals differ, scientists will need to examine DNA from the Neandertal’s entire genome. The sequence reported in the new study was generated as part of a project to decode Neandertal DNA, but it contains information only about DNA from mitochondria.

Mitochondria are organelles that generate energy for a cell. Inside each mitochondrion is a circular piece of DNA that contains genes encoding some of the key proteins responsible for power generation. Mitochondria are passed down from mothers to their children. Scientists use variations in mitochondrial DNA as a molecular clock to tell how fast species are evolving.

Scientists have previously examined a short piece of Neandertal mitochondrial DNA known as the hypervariable region, but this new complete sequence helps clear up some ambiguities from studies comparing Neandertals and humans, says John Hawks, a biological anthropologist from the University of Wisconsin–Madison.

Some modern humans have several changes in the hypervariable region that made it seem as if Neandertals are more closely related to modern humans than humans are to each other.

“Comparing the complete mitochondrial DNA genomes of a Neandertal and many recent humans presents a very different picture,” Hawks says. “Humans are all more similar to each other, than any human is to a Neandertal. And in fact the Neandertal sequence is three or more times as different, on average, from us as we are from each other. This change from the earlier picture is a purely statistical one, but it makes a clearer picture.”

Human and Neandertal mitochondrial DNAs differ at 206 positions out of the 16,565 examined, while modern humans differ at only about 100 positions when compared with each other.

UK News:

A period of prehistoric global warming and not the decline of the dinosaurs could be responsible for the rise of mammals, it was claimed today.

Scientists have drawn up a new “tree of life” tracing the history of all 4,500 mammals on Earth which shows they did not spread as a result of the massive asteroid strike that killed off the dinosaurs 65 million years ago.

Most palaeontologists believe the extinction of T Rex and his terrifying cousins permitted our ancestors to flourish and begin the long evolutionary process culminating in the diverse array of species we see today.

But an international team of researchers, which has taken more than a decade to chart modern mammals from existing fossil records and new molecular analyses, show many of the genetic ‘ancestors’ of the mammals existed 85 million years ago – and survived the meteor impact that is thought to have wiped out the dinosaurs.

However, throughout the Cretaceous period 144 to 65 million years ago, when dinosaurs walked the earth, these mammal species were relatively few in number and were prevented from diversifying and evolving in ecosystems dominated by dinosaurs.

The tree of life published in Nature shows after the asteroid strike certain mammals did experience a rapid period of diversification and evolution.

But most of these groups have since either died out completely such as Andrewsarchus – an aggressive wolf-like cow – or declined in diversity such as the group containing sloths and armadillos.

The researchers believe our ‘ancestors’, and those of all other mammals on earth now, began to radiate around the time of a sudden increase in the temperature of the planet – ten million years after the death of the dinosaurs.

Biologist Professor Andy Purvis, of Imperial College London, said: “Our research has shown for the first 10 or 15 million years after the dinosaurs were wiped out present day mammals kept a very low profile while these other types of mammals were running the show.

“It looks like a later bout of ‘global warming’ may have kick-started today’s diversity – not the death of the dinosaurs.

“This discovery rewrites our understanding of how we came to evolve on this planet – and the study as a whole gives a much clearer picture than ever before as to our place in nature.”

Abstract of Nature article.

Hat tip to José Guardia

Paleontologists excavating in the Riversleigh Fossil Beds (also) in Northern Australia have made some exciting finds:

Palaeontologists digging in northern Australia claim to have found the fossilised remains of the ultimate fighting marsupial – a flesh eating “killer kangaroo” that had wolf-like fangs and once walked the earth more than 10 million years ago.

The team from the University of New South Wales made the discovery along with 20 other previously unknown species in northern Queensland, including the carnivorous kangaroo, known as Ekaltadeta, and a large predatory bird described by the team as a “demon duck of doom”.

The vertebrate palaeontologist Sue Hand said the meat-eaters would have looked remarkably different from kangaroos around today. “These things had slicing crests that could have crunched through bone and sliced off flesh,” she said.

Professor Michael Archer, another team member, described the remains of two kangaroo species, one with wolf-like fangs and another with long forearms that was unable to hop like a modern kangaroo. “Because they didn’t hop, these were galloping kangaroos, with big, powerful forelimbs. Some of them had long canines like wolves,” he said.

The killer marsupial and duck of doom flourished in the Miocene epoch.

The discovery of a new fossil in China, Castorocauda lutrasimilis, demonstrates that mammals appeared early, and in larger forms, than previously believed, living at the same time as dinosaurs.

The San Francisco Chronicle story reports:

The remarkable fossil bones of a fur-covered, swimming mammal that lived in the age of the dinosaurs 164 million years ago have been discovered in China, raising a wave of excitement among scientists whose timetable for mammalian evolution has just been pushed back by 100 million years.

The animal appears to have been more than a foot long and weighed nearly 2 pounds, with a tail remarkably like a beaver and seal-like teeth clearly adapted for catching and eating fish, its discoverers say…

..The furry mammal was found in a rich fossil bed in Inner Mongolia’s Ningcheng county, about 160 miles northeast of Beijing. Its nearly complete skeleton was extracted from a rock layer along with the bones of small, two-legged meat-eating dinosaurs, primitive winged reptiles and the abundant remains of long-extinct crustaceans.

The rocks encasing the fossil skeleton bore the clear imprint of the dense hairs that had covered its body when it died in the mud and the horny scales that covered its flattened tail, the scientists said. They named their animal Castorocauda lutrasimilis and said it must have resembled a modern river otter or the “duck-billed” platypus of Australia.

William Clemens, professor emeritus at UC Berkeley and a former director of the Museum of Paleontology there, said the discovery provides “really good evidence” that the animal was both a swimmer and a fish-eater.