Recessive X’s are not so quiet

Punnet square for a gender conferred recessive trait.

Two X chromosomes (XX) makes women female. Men have an X and a Y, the latter of which is responsible for all the things that make them male. What we teach is that one of the X’s in the women’s XX’s dominates the other so that women’s physical characteristics (phenotype) is only determined by the dominant X. Recent research shows that’s not necessarily the case.

“Our study shows that the inactive X in women is not as silent as we thought,” said Laura Carrel, Ph.D., assistant professor of biochemistry and molecular biology, Penn State College of Medicine, Penn State Milton S. Hershey Medical Center. “The effects of these genes from the inactive X chromosome could explain some of the differences between men and women that aren’t attributable to sex hormones.” – From Penn State University, edited by Science Daily.

It’s a fascinating finding, but I don’t think I’ll go into it with the students except, in the very unlikely event, that a direct question comes up. At this point, simpler is better.

The cynic’s guide to argument

This guide, from a longtime commenter on Megan McArdle’s blog, does an excellent, if cynical, job of explaining how to win an online argument. It includes:

  • Using allusions to make you look smarter (Wikipedia is a great resource for finding quick facts).
  • Treating stupid questions as if they are serious (this one could actually help the conversation).
  • Treating serious questions as though they’re stupid (great way to score points, but do not contribute to a good discussion).
  • Admitting any and all faults you are accused of (this diffuses the bottom two argument styles in Graham’s hierarchy: name-calling and ad-hominem attacks.)
  • Asking earnest questions instead of making arguments (which can be very useful in pointing out the complexities of a situation.)
  • Never pulling rank. Let your credibility (ethos) be based on what your argue, not on how much education/training/experience you have (credibility is important, and so is experience, but pulling rank tends to annoy people and that will loose you friends.)
  • Being brief (snappy one-liners may not have the depth of a well reasoned argument but are more likely to win friends).

Most of these techniques are appeals to the emotions (pathos). They can, and may sometimes need to, be used to support a good, well reasoned, argument (logos).

[B]efore some audiences not even the possession of the exactest knowledge will make it easy for what we say to produce conviction. – Aristotle in On Rhetoric

Be careful how you use these things, and watch out for them, because they don’t only occur online, you’ll see them often in any conversation.

Voyage of the Beagle

Wired has a brief but excellent article on the voyage of the Beagle.

Its goal was to survey the South American coastline. The captain invited along a young man named Charles Darwin, whose father thought the voyage would just be another excuse for him to slack off. The trip ended up taking five years.

This article would be a wonderful addition to our work on exploration of the Americas next time it comes around; however, it’ll also be a neat little footnote because we’ll be delving into evolution next cycle.

Wikipedia’s entry on the ship produced this wonderful cross-section. I particularly like the sketches of people and casks showing the use of of different cabins and spaces.

Cross-section through the HMS Beagle.

Homo sapiens neanderthalensis?

In the binomial classification, modern humans are Homo sapiens (Genus and species). But you’ll frequently see us described as Homo sapiens sapiens, indicating that we’re a subspecies of Homo sapiens. One of the reasons for this is the still unresolved question of the neanderthals.

Some recent research suggests that 1-4% of our genes came from neanderthals. If true, this would mean that humans interbred, successfully, with neanderthals. Since one of the key parts of the definition of a species is that its members can produce fertile offspring, neanderthals would then be a subspecies of human. Thus we would be Homo sapiens sapiens and neanderthals would be Homo sapiens neanderthalensis, as opposed to being Homo neanderthalensis, a separate species in the same genus.

Skull differences between sapiens and neanderthalensis. Image by hairymuseummatt.

Perhaps even more interesting, the same researchers who did the gene work on neanderthal bones also sequenced some bones from Siberia, and found what may well be another subspecies of humans (the original article is at Krause et al., 2010). The genes are different from what’s been found before, but are in an area, and from a time period, shared both by modern humans and neanderthals. And, modern Melanesians (from the islands north and east of Australia) may share some of the genes of the new group. So this could even be another sapiens subspecies.

There are a number of caveats to this research, which is based primarily on gene sequencing and statistics. One key assumption that I’ve always been skeptical about is that DNA mutates at a fixed rate. However, this type of science ties very closely in to our discussions of evolution and themes of what it means to be human.

There are two great novels that address these two things, but I’ll only be using one of them. The one I’ll use is The Chrysalids by John Wyndham, which I’ve mentioned before (here and here). The other is War Games by Brian Stableford (aka Optiman). While the Chrysalids deals with accelerated mutation resulting from nuclear fallout, War Games considers the effects and moral implications of intentional genetic optimization (hence the other title for the book).

Critical Reading

With the exception of informed ones, opinions have little use as supporting evidence. – Critically Evaluating the Logic and Validity of Information from Cuesta College.

Cuesta College has a nice but fairly dense webpage on, “Critically Evaluating the Logic and Validity of Information“.

It starts with distinguishing between facts and opinions, goes into evaluating arguments and rounds up with asking critical questions. There’s lots of good information, but it needs to be parsed, broken apart, and condensed for middle school students.

Facts are statements that can be verified or proven to be true or false. Factual statements from reliable sources can be accepted and used in drawing conclusions, building arguments, and supporting ideas.

Opinions are statements that express feelings, attitudes, or beliefs and are neither true nor false. Opinions must be considered as one person’s point of view that you are free to accept or reject. With the exception of informed ones, opinions have little use as supporting evidence, but they are useful in shaping and evaluating your own thinking. [My emphasis]
Critically Evaluating the Logic and Validity of Information from Cuesta College.

This can be tied in with my previous notes on Paul Graham’s Hierarchy of Disagreement to create a set of lessons on critical thinking and evaluation.

Paul Graham's Hierachy of Disagreement (image adapted from Wikipedia).

Sex. Ed. on TV update

The National Campaign to Prevent Teen and Unplanned Pregnancy has recently issued a report showing that teen pregnancy dropped by 6% in 2009. They have some evidence that the TV show “16 and Pregnant”, which I’ve mentioned before, is one of the reasons why.

Among those teens who have watched MTV’s 16 and Pregnant, 82% think the show helps teens better understand the challenges of teen pregnancy and parenthood and how to avoid it.
Albert (2010)

Of course, it’s essential to note that, “Teens (46%) say parents most influence their decisions about sex.”

The report has many more details.