Tuesday, March 27, 2007

Marmosets: who's who?

Now, this is something I had never heard of before that is just too weird/crazy/cool not to blog about. Apparently, female marmosets (small South American primates) normally give birth to fraternal twins. Kind of quirky, but nothing too shocking there. However, it turns out that during early fetal development, the twins swap lots of stem cells. Twin A gives some stem cells to Twin B; Twin B gives some stem cells to Twin A. These stem cells then go on to differentiate into various other types of cells, tissues, and organs. So, a single marmoset is actually a mixture of two different sets of DNA - a phenomenon known as chimerism (named after the mythological creature Chimera - a beast made up of multiple animal parts).

Scientists have also found that almost half of male marmosets actually carry two lineages of sperm, and in some rare cases, females can carry two lineages of eggs. This means that some of their gametes are genetically NOT THEIR OWN, but instead are genetically their sibling's. If you will allow a somewhat crude elaboration, this means that a male may fertilize an egg with his brother's sperm, thereby siring not his own child, but his niece or nephew. Likewise, it is possible that a female could give birth to her niece or nephew and not her son or daughter. Genetically speaking of course.

Told you it was wierd/crazy/cool.

Read more:
NY Times article

Tuesday, March 20, 2007

March Madness, Geek Style

Just in case there was any question about my geek status, here's a link to something I am finding all too entertaining - the Science Spring Showdown. Basically it's an NCAA-basketball-tournament-style science playoffs. Complete with game breakdowns and news items (see the controversy surrounding Surgery's Internal Medicine's disqualification). I'm partial to the Octopus Bracket myself and must admit that I am fully pulling for the #1 seed, the Invertebrates. If only I had found this site before the games had begun - there's even a printable bracket to fill out.

Who's your Final Four?
(is ANYONE here any more?)

Science Showdown 2007

Friday, March 09, 2007

Evolution essay contest - win $300

I'm a bit late finding this out, but the Alliance for Science is holding an essay contest for high school students. First prize is $300. The topic of the essay is: "Why would I want my doctor to have studied evolution?" and it is due March 31st.

Details can be found here

At first glance this seems like a silly question, but you would be amazed at the number of doctors who are "anti-evolution". I'm amazed that there are any at all. A good summary of physicians vs. evolution can be found here

I know March 31st is approaching quickly and that you have plenty of things on your plate, but I also thought you might like to know about a chance to use your knowledge of evolution to win $300. Let me know if anyone decides to enter the contest.

Thursday, March 08, 2007

Yes, it's a worm.

The Monterey Bay Aquarium Research Institute has an interesting piece on the discovery of a new deep-sea worm. This worm, Chaetopterus pugaporcinus, is unlike any worm you have probably ever seen. In fact, it was unlike any worm anyone had ever really seen. To figure out what exactly it was, scientists needed to combine a number of taxonomic techniques, including DNA analysis. What makes this discovery particularly interesting is that it resembles the larval stages of closely-related species, but is up to 10x larger than any known larvae - so either it is an adult that has maintained larval features or it is one giant baby (well, giant as far as deep-sea worms go).

Also rather interesting is where and how this worm lives - floating along 1,500 meters (4,000 feet) below the surface, mouth pointed downward so it can release a "mucus cloud" to trap bits of food (lunch anyone?). Follow the links below to the discovery and more photos and to the Monterey Aquarium website.

A worm like no other

Monterey Bay Aquarium Research Institute (MBARI) website

Monterey Bay Aquarium website - if you're ever near Monterey, CA you definitely need to check this place out

Saturday, March 03, 2007

An Inconvenient Truth

I finally saw An Inconvenient Truth last night. I thought it was very well done and if you haven't seen it yet I highly recommend that you do, especially if you don't know too much about the causes and effects of global climate change. The message is good and clear, the visuals are impressive, Al Gore is at his best, and even the music is well done. I've seen and read about all the data before, but Al Gore does an excellent job of presenting them in a user-friendly, yet not dumbed-down way. Americans have for too long now been wavering on the topic of global warming - is it real? are we really the cause? what could possibly happen if it gets a little warmer? Well: yes, yes, and a lot. It is time we all took a long hard look at ourselves and the way we live and make some changes.

I'll get off my soap box now. Seriously though, go rent this movie. And check out the website:

An Inconvenient Truth

Friday, March 02, 2007

Galapagos: set your TiVo

On March 18, the National Geographic Channel is premiering a three-part documentary on the Galapagos that looks like it should be excellent. The islands are an amazing place and I'm willing to bet that National Geographic does an incredible job with the show, so I would recommend tuning in for it. (The photo here is a Sally Lightfoot Crab - taken by yours truly)

Added bonus: check out
the show's website and enter to win a 10-day trip to the Galapagos!

UPDATE - 3/20/07: I watched the first two hours and was impressed with the footage and the information. Some of the narration is a bit schlocky, but I guess that can be forgiven. There is one piece that I found humorous in a way - when they speculate on "what might have happened" if Darwin had paid closer attention to the tortoises as if then he REALLY may have come up with some intereting ideas. Cause man, it's a shame that he didn't really notice those tortoises and had to settle for causing a major paradigm shift in modern science and influencing the future of biology, religion, and human culture. Just think what he could have done if he collected some tortoises. Seriously though - it's a well done series and you should definitely check it out if for no other reason than to ooh and aah at the visuals.

Thursday, March 01, 2007

Milk: a driving force of evolution?

How many of you are lactose-intolerant? If you are, no need to fret - it's the normal mammalian trait to have.

As you know, lactose is the sugar found in milk, and lactase is the enzyme that helps break it down. Mammals obviously have a need for lactose and the production of lactase - after all, one of the defining mammalian characteristics is that moms produce milk as nourishment for their young. If a mammal is born without the ability to produce lactase, chances are they're going to have a hard time surviving. But, eventually, mammalian babies grow up and wean. For all mammals but us, this is the last time they ever drink milk. Thus, most mammals stop making lactase as they get older - what's the point of spending energy to make an enzyme you don't need anymore. Therefore, most adult mammals are lactose-intolerant.

But a curious thing happened during human history - the domestication of cattle, goats, and sheep. Being able to digest milk became beneficial in adults. So, as you could guess, natural selection has pushed adult humans towards lactose-tolerance. A new study has actually determined that the evolution of adult lactase production in humans happened as recently as 8,000 years ago. This is way after the evolution of Homo sapiens. In fact, by this time most of the globe had been settled by modern humans and various ancient cultures were beginning to establish themselves. Thus, it is likely that lactose-tolerance evolved in only some places, or it evolved multiple times independently. Lactose intolerance is least common in people of Northern European descent, while 80% or more of African-Americans, Asian-Americans, and Native Americans are lactose intolerant - these numbers are probably consistent with if, when, and how much these groups' ancestors utilized domesticated milk sources (though I don't know this for sure).

For some of our ancestors, milk has been a strong evolutionary force - it only took 8,000 years to evolve lactose tolerance (yes, only 8,000 years).

Evolution: It Does a Body Good

Ancient Human Timeline

update on 2/2/07: Just found a blog entry by Carl Zimmer discussing this topic as well.