Why assault weapons?

February 28, 2013 • 5:37 am

California Senator Dianne Feinstein has introduced into the U.S. Congress proposed legislation that would ban military-style assault weapons. The weapons proposed for banning are semiautomatics, those having large magazines and that fire one round each time you pull the trigger, automatically ejecting the spent cartridge and loading the next into the chamber. You don’t have to reload until many bullets have been fired. Here’s one of them, the An Intratec TEC-DC9 with a 32-round magazine. It’s legal:

Kg99

What possible civilian use can such a weapon have? Certainly not for hunting, and if you want to protect yourself or an intruder, there are handguns and rifles with smaller stores of ammo or bolt action reloading.

Sadly, the Republicans in Congress (under pressure from the National Rifle association) oppose this, and it is unlikely to pass. Other pending legislation requiring background checks of gun purchasers, including those at gun shows, has also been stalled because of Republican opposition.  These two initiatives are part of President Obama’s push to tighten up gun laws and make it harder to conduct mass killings like those at Newtown. That too, will amost certainly fail.  As the Los Angeles Times reports:

Although negotiations continued, no progress on background checks appeared evident in the Senate, where a bipartisan group struggled over how to broaden them. The major sticking point: whether private citizens who sell guns directly to others should be required, like licensed dealers, to keep records of the sale.

Gun rights backers warn those records could be used to create a national registry of gun owners, which they oppose.

Sen. Tom Coburn (R-Okla.), one of the key negotiators, said this week that any provision that required gun owners to keep records would “kill this bill.” Instead, he said, legislation should give sellers “the right and the responsibility to do the right thing” and run a background check.

Gun control advocates say that without a paper trail, it’s impossible to know whether background checks have been performed, opening a loophole for criminals to buy guns.

And without a paper trail it’s hard to trace back weapons used in assaults.

Here’s a summary of Feinstein’s Assault Weapons ban of 2013 from her website:

The legislation bans the sale, transfer, manufacturing and importation of:

  • All semiautomatic rifles that can accept a detachable magazine and have at least one military feature: pistol grip; forward grip; folding, telescoping, or detachable stock; grenade launcher or rocket launcher; barrel shroud; or threaded barrel.
  • All semiautomatic pistols that can accept a detachable magazine and have at least one military feature: threaded barrel; second pistol grip; barrel shroud; capacity to accept a detachable magazine at some location outside of the pistol grip; or semiautomatic version of an automatic firearm.
  • All semiautomatic rifles and handguns that have a fixed magazine with the capacity to accept more than 10 rounds.
  • All semiautomatic shotguns that have a folding, telescoping, or detachable stock; pistol grip; fixed magazine with the capacity to accept more than 5 rounds; ability to accept a detachable magazine; forward grip; grenade launcher or rocket launcher; or shotgun with a revolving cylinder.
  • All ammunition feeding devices (magazines, strips, and drums) capable of accepting more than 10 rounds.
  • 157 specifically-named firearms (listed at the end of this page).

The legislation excludes the following weapons from the bill:

  • Any weapon that is lawfully possessed at the date of the bill’s enactment;
  • Any firearm manually operated by a bolt, pump, lever or slide action;
  • Assault weapons used by military, law enforcement, and retired law enforcement; and
  • Antique weapons.

The legislation protects hunting and sporting firearms:

The bill excludes 2,258 legitimate hunting and sporting rifles and shotguns by specific make and model.

My question is this:  why is there any reason for civilians to own such weapons? They’re not for hunting, and, as I noted, you can protect yourself without huge-magazine semiautomatic weapons. They have only one use: to kill large numbers of people.

How is the possession of such weapons justified? I know that the “background-check” legislation is opposed because of the ridiculous idea that it would put America on a slippery slope, at the bottom of which is complete prohibition of all guns for civilians (something that I favor, by the way).  But that argument is ridiculous: you can ban alcohol for those over 18 without that leading to a total ban on alcohol.

But are assault weapons defended with the same “slipperly slope” argument? (I doubt that, because we already have a ban on fully automatic weapons, and that hasn’t led to complete prohibition of guns.) Or is there some argument I don’t know that even a stupid Republican can offer in defense of these weapons?

The Republican Party is not only the party of the rich, but the party of mass killings. It favors a dysfunctional America, and I wouldn’t be upset if every Republican in Congress lost their seat.

Ice age art

February 28, 2013 • 5:08 am

Perusing the latest stuff from the journal Nature, I found this lovely video of a new exhibit at the British Museum featuring some of the oldest artwork known—including pieces made 40,000 years ago. That’s not too long after the “out of Africa” event that spread modern Homo sapiens through the world! Take a look at the “lion man” in the first clip

Here are the movie notes. If you’re in England, go see this, though it costs ten pounds to enter (note, though, that the rest of the British Museum is free).

A new exhibition at the British Museum in London features sculptures made up to 40,000 years ago. Dr. Alice Roberts meets curator Jill Cook to discuss three artefacts in the collection; the Lion Man, a group of female figurines from Siberia, and the oldest known musical instrument. Despite being made thousands of years ago, the objects show that the minds of their creators – our ancestors – were incredibly similar to our own.

When the flute shown in the video was first discovered the finding was published in Nature: New flutes document the earliest musical tradition in southwestern Germany.
‘Ice Age art: arrival of the modern mind’ runs at the British Museum until 26 May 2013. http://www.britishmuseum.org/whats_on…

Here are some pieces from the BM’s website on the exhibit; they (and the video above) show that there were already accomplished artists tens of thousands of years ago.

The oldest known portrait of a woman sculpted from mammoth ivory found at Dolní Vestonice, Moravia, Czech Republic. approximately 26,000 years old
The oldest known portrait of a woman; sculpted from mammoth ivory found at Dolní Vestonice, Moravia, Czech Republic. approximately 26,000 years old
Spear thrower made from reindeer antler, sculpted as a mammoth. Found in the rock shelter of Montastruc, France. Approximately 13,000–14,000 years old
Spear thrower made from reindeer antler, sculpted as a mammoth. Found in the rock shelter of Montastruc, France. Approximately 13,000–14,000 years old
Tip of a mammoth tusk carved as two reindeer depicted one behind the other. Approximately 13,000 years old, from Montastruc, France
Tip of a mammoth tusk carved as two reindeer depicted one behind the other. Approximately 13,000 years old, from Montastruc, France

OMG: a squirrel builds its nest on my windowsill

February 27, 2013 • 1:35 pm

For the past few days I’ve been hearing scuttling noises outside my window. Since I keep the blinds closed by my desk, as the sunlight makes it hard to see my computer, I thought it was just snow or ice falling off the roof. Yesterday, however, I opened the blinds because the noise was insistent.  And, lo and behold, I found an eastern gray squirrel (Sciurus carolinensis) building a nest on my windowsill.  It (sex is indeterminate yet, and both sexes build nests) is breaking off stems of Virginia creeper to make the framework, and rearranging the twigs in what seems to be a haphazard manner (I’m sure there’s method in its madness, though).

squrl 2

I’m not sure why this crazed rodent was building a nest in the middle of a snowstorm, but maybe it’s preparing for baby season. I thought that squirrels also built nests to protect them from winter’s ravages, and it’s a bit late for that.

Sqrl 1

Right now there’s just a roughly circular pile of twigs, which the frenetic squirrel supplements and rearranges at random times.

I will of course keep readers updated on what happens next.

How to make Abe happy or sad

February 27, 2013 • 11:42 am

When I first saw this picture of a folded $5 bill showing LOLzy modifications of Abe Lincoln, I thought it was a fake.

972

But of course I had to try it myself, and, sure enough, it worked.  You just make one crease right down the middle of the bill, bisecting Abe’s nose, and then two creases in the opposite direction through Abe’s eyes. Then, viewing it from different angles, you get the effect.

The bill, flat as usual:

P1000281

Happy Abe:

happy

Sad Abe:

sad

Now you too can be the life of the party!

Another case of individual selection trumping group selection

February 27, 2013 • 8:36 am

I’m teaching introductory evolution this quarter, and am using as a textbook Doug Futuyma’s Evolution (second edition, Sinauer). Today’s lecture will be on the maintenance of genetic variation via natural selection (heterosis, etc.), and in the textbook under “frequency dependent selection,” I see this on page 319:

Why is the sex ratio about even (1:1) in many species of animals? This is quite a puzzle, because from a group-selectionist perspective, we might expect that a female-biased sex ratio (i.e., production of more females than males) would be advantagesous because such a population could grow more rapidly. [JAC: such a sex-ratio-biased group would then outcompete other groups and predominate]. If sex ratio evolves by individual selection, however, and if all females have the same number of progeny, why should a genotype producing an even sex ratio have an advantage over any other?

The answer, first realized by Ronald Fisher in 1930, is that there is individual “frequency-dependent” selection that enforces an even sex ratio. Consider, for instance, a population in which females predominated, and males were rare. In that population, a female who produced more males would have more grandchildren than other females, for the average reproductive success of her offspring will be higher. (Imagine if there were only one male and elebenty gazillion females in a population. A mutant female producing mostly or all males would have huge numbers of grandchildren, for her male offspring would inseminate most of the females. Evolutionarily, whatever genes gave her that male-biased sex ratio would increase in the population.)

The reverse would be the case if males predominated in the population: any mutant individual producing more females would leave more grandchildren.

In this case, then, the rarer sex always has a reproductive advantage, and any variant individual producing the rarer sex would have an evolutionary advantage. The upshot is that the sex ratio will reach equilibrium only when there IS no rarer sex, i.e., when there are equal numbers of males and females. In such a case no new mutant individual will have a reproductive advantage.  This has been tested experimentally by varying sex ratios in species which have three sex chromosomes, and populations always settle down at the 50/50 sex ratio.

Although there are some exceptions to a 50/50 sex ratio in animals, most conform to the 50/50 value. This is precisely what is expected if sex ratio is a result of individual and not of group selection. Ergo, when the two are in evolutionary conflict, as they are here, individual selection wins.  And evolution is the answer to a question you’ve probably never asked yourself: why are there as many females as males?

I still know of no adaptation in nature that is explained more plausibly by group selection than by individual or kin selection; but there are plenty of adaptations, like sex ratio, easily explained by individual or kin selection.

It’s time for biologists to stop banging on about group selection until we find evidence that it has actually operated in nature. We don’t have time to waste on theoretically plausible but infrequent mechanisms for which there’s no evidence.

Buzzsaw!: An ancient spiral-toothed shark

February 27, 2013 • 6:43 am

Imagine an ancient shark with a single spiral tooth, shaped like a buzzsaw, in its lower jaw.

That’s what’s reported in a new paper in Biology Letters by Leif Tapanila et al. (free download).  The spiral-like structure of this fossil, Helicoprion, had been known for some time, but it was curious: what seemed to be a single serrated tooth in the shape of a logarithmic spiral. Biologists had wondered how it was placed in the jaw, how it was used, and even if it was a tooth rather than some other part of the body.

This is what the structure, now known from the paper to indeed be a tooth, looks like (all photos and drawings from the paper):

Helicoprion specimen IMNH 37899, preserving cartilages of the mandibular arch and tooth whorl. (a) Photograph and (b) surface scan of fossil, positionedanterior to the right, imbedded in limestone slab.
Helicoprion specimen IMNH 37899, preserving cartilages of the mandibular arch and tooth whorl. (a) Photograph and (b) surface scan of fossil, positioned
anterior to the right, imbedded in limestone slab.

The authors did CT scanning of a fossil found in 1950 in Idaho, dated to the early Permian—about 270 million years ago.  The tooth, fortuitously, was embedded in the remains of the skull, something that’s rare because sharks have cartilage instead of bones in their skeleton. (That’s why shark teeth are so much more common in the fossil record than sharks themselves.) Using scans, they were able to show the placement of the teeth in the jaw.

Here’s a model, based on the CT scan, of the tooth placed in the mouth, taken from the side (lateral position):

Picture 3

And an oblique view from the side with the position of tooth interpolated from the scan:

Picture 4

(For you readers who know anatomy, here’s the key: bp, basal process; c, cup-shaped portion oflabial cartilage; ep, ethmoid process; lj, labial joint with base of root; pf, lateral palatine fossa; pp, process limiting jaw closure; qf, lateral quadrate fossa;qmf, quadratomandibular fossa; qp, quadrate process.)

The tooth apparently grew continuously, and, as the shark’s mouth closed on its prey, could be rotated up and back, cutting the prey and forcing it into the back of the mouth.  BBC Nature interviewed the first author and gives more information:

Using the computer images, the team could build a 3D model of the jaw, to reveal how the tooth spiral worked.

“As the mouth closes, the teeth spin backwards… so they slash through the meat that they are biting into,” Dr Tapanila told BBC Nature.

“The teeth themselves are very narrow: nice long, pointy, triangular teeth with serrations like a steak knife.

“As the jaw is closing and the teeth are spinning past whatever it’s eating, it’s making a very nice clean cut.”

What could those teeth be used to eat? The answer is rich (P. Z. take note):

Dr Tapanila said that this evidence, combined with the “rolling and slicing” mechanism, provided clues to what the ancient fish ate.

“If this animal were eating other animals that were very hard or [had] hard armour plating or dense shells, you would expect more damage to their teeth.

“This leads us to believe that our animal was probably eating soft, squishy things like calamari. It was probably eating squid or its relatives that were swimming in the ocean at the time.”

As the paper reports, the spiral teeth are involved with a suite of other skull adaptations. Anatomy buffs take note:

Retention of teeth in a continuously growing whorl necessitates specialized morphologies, including the buttressing labial cartilages to maintain rigidity and alignment of the whorl, as it occludes between the upper jaws. With the jaw articulation next to the whorl, closure of the lower jaw rotates the teeth dorsoposteriorly, providing an effective slicing mechanism for the blade-like serrated teeth and forcing food to the back of the oral cavity.

Accommodating the continuous growth of the logarithmic whorl required commensurate anterior and dorsal expansion of the mandibular arch to house the symphyseal structure. Based on the largest diameter whorls in the IMNH collections, Helicoprion jaw length and height could exceed 50 cm, nearly double the size of IMNH 37899. Pre-mortal tooth wear or breakage is rare in Helicoprion [5,6]. This may be a result of rapid tooth production—some whorls exceed 150 [cm.!]—along with prey selection of soft-bodied animals, such as cephalopods [6] or poorly armoured fish.

I’m sure you’re probably wondering what the animal looked life in life. Here’s a reconstruction from the paper:

Picture 1

UPDATE: Reader gb james, in the comments below, points out a longer National Geographic article on the species with more pictures. Here’s one:

HelicoProfileWithWhorl_color

h/t: Dom

_______________

Tapanila, L., J. Pruitt, A. Pradel, C. D. Wilga, J. B. Ramsay, R. Schlader, and D. A. Didier. 2013. Jaws for a spiral-tooth whorl: CT images reveal novel adaptation and phylogeny in fossil Helicoprion. Biology Letters 9:10.1098/rsbl.2013.0057.