Conversation between two apes explained

My chimp/chump story from last week is a simplified example of how one ape species split into two.  This splitting is called speciation.  The apes in the story are members of the species that was the most recent common ancestor of humans and chimpanzees (and bonobos.)

Let’s pause for one of the digressions I like to call drum solos.  Don’t think you have ever heard of bonobos?  Sure you have.  Remember that thing about a kind of chimpanzee that resolves its differences by having sex?  That’s the bonobo, but they actually are a separate species from chimps.  They split off from chimps after we did.  Thanks, Mickey

Why five million years ago?  We infer that date from several pieces of evidence.  We have 4.4 million year old fossils of creatures called australopithecines, who are our ancestors, but not chimp ancestors.  The split must have happened before then. 

DNA provides the link we have yet to find in the fossil record.  We know how quickly DNA mutates on average.  We count the differences between human DNA and chimp DNA to calculate the number of years it should take for those differences to accumulate.  The answer is five million years. 

We feel confident in the five million year figure because this method was also used to calculate the date of our split from orangutans.  The fossil record confirms that the orangutan date is correct so we know the method works.

Now that we know when the human-chimpanzee split happened, we might wonder why it happened then.  Five million years ago was the end of a harsh cold snap.  Africa was colder and drier than it had been so the forests were breaking up and turning into woodlands.  We all know about the mass extinctions at the end of the Cretaceous period.  Climate changes killed off the dinosaurs and many other animals and gave the mammals a chance.  Or when the internet liberated music and all music became free and corporate music died and only the most talented bands… OK, bad example. 

The point is that environmental changes can drive evolutionary change.  This is what happened five million years ago.  It was getting really competitive in the trees.  Those who were above average at tree living were more likely to survive to reproduce.  Those who could make it elsewhere were also more likely to reproduce.  Those who reproduce are likely to pass along whatever advantages they have to their children.  The advantages don’t have to be very big to have a large effect.  Even small advantages will become more common over a number of generations. Future mutations will increase existing advantages or create new ones.  The mutations eventually add up to a huge change. It’s important to remember that this takes place over a very long time.  It’s not like in the Ringo Starr movie Caveman in which people go from walking bent-over to walking fully upright in a minute. 

If, as in this story, the proto-chimps stay in the trees and the proto-humans live on the ground, the two groups will stop inter-breeding.  Eventually, so many differences will accumulate that the two groups can no longer inter-breed.  Then we say that speciation has happened. 

We will give speciation five Lemmys because we wouldn’t even be here without it.

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“Fun” science quiz turns into religious debate

The USA Today published a nice little “Test Your Science Savvy” quiz as a sidebar to an article about scienfic literacy in the US.  The quiz is a fun test of very basic science knowledge.  Questions on The Big Bang, Evolution, and the age of the Earth set off a religious debate. 

For me, the core of the article is here

“We have in this country a major crisis of people listening to people they feel comfortable with (rather than) listening to a variety of groups and critically thinking through their messages,” says Gerry Wheeler, executive director of the National Science Teachers Association.

I think that explains the comments from folks who appear to be getting their ideas about science from non-scientific sources. 

It also contains a lesson for those who express frustration with people who prioritize religious over scientific teachings.  Listening to religious folks will help science writers find ways to explain the world without pushing people’s buttons. 

The Centers for Disease Control and Prevention has a successful example of this on their page on Influenza.  They explain that flu shots are necessary every year because the flu virus changes.  Note that they don’t use the word “evolve.”  That could be for political reasons, but it’s also good because use of that word will distract people.  The purpose of that web page is to give medical advice, not to piss people off.  People don’t take advice when they are pissed at you.

I give the quiz Five Lemmys.  It was fun, pushed people’s buttons (as something that truly rocks will), and  told us something we might not have expected to learn.

What kind of man defaces a defenseless textbook? What do you want to do with your life?

My inner 17-year-old is surprised to read this, but I am an “old school” parent—my wife and I make all family decisions. Some families may be democracies and I personally know two families that are ruled by six-year-old girls. I am not saying my wife runs our house like a military academy. Our kids don’t have to eat everything on their plate, but we decide what is for dinner.

This approach works best for our family. The extra freedom we used to give our older son overwhelmed him. Asking him whether he would prefer black beans or chickpeas for lunch stressed him out with an unwelcome and unnecessary distraction. He has better things to do than worry about the menu and is happier when we decide for him.

There is a biological explanation for this behavior.

We normally think of natural selection affecting our physical structure. Why do peacocks have those big colorful tails? Peahens prefer them–probably a lot– because large tails are a big disadvantage. You need to eat more if you want a big tail and that could be a problem when food is scarce. Also, I’m sure that tigers appreciate the large colorful heads up that dinner is served.

Natural selection can also select tendencies for certain behaviors over other tendencies. One of those behaviors is to believe without question things that our parents and authority figures tell us. If your parents say, “Stay back from the edge of that cliff!” or “Spit out that red berry!” you are pretty likely to do as they say. This is because your ancestors also were likely to listen to their parents. The kids who didn’t listen fell off cliffs or poisoned themselves and didn’t pass along their “you’re not my boss” genes.

Just as a peacock’s tail has the unfortunate consequence of making peacocks easier to spot by predators, our inclination to believe authority figures no matter what sometimes gets us in trouble. Religious suicide cults are an extreme example. My dad told me (sarcastically, I hope) that even though an hour starts when the minute hand is on the twelve, a minute begins when the second hand is on the nine. I thought that was odd, but it didn’t occur to me to question it. I believed it for fifteen years until I actually said it out loud and logic took over.

Luckily for me, when a minute starts never came up. Unluckily for me, politicians, sales people, and ad execs frequently try to fool me because they know I am inclined not to question authority figures. They are successful sometimes but I swear that I have never bought anything from QVC.

Watch the intro to this Twisted Sister video and you’ll see where I’m going.

Digression for musical history: If you weren’t around in the 1980s, there was a big difference between metal fans then and the last fifteen years of metal fans. Recently, metal fans are supposed to be in shape and with nice tattoos. They are cool and their girlfriends look like Amy Lee from Evanescence. Back in the day, the real metal fans I knew were more like the kid in this video. They wore their coats all year long–even in gym–and didn’t really talk to anybody.

(Actually, they did talk to me. I got to know them when I wound up in remedial gym class. Some of them were pretty good at volleyball. Remedial gym was fun. Once you get rid of the guys who have something to prove the freaks who have nothing to lose can have a good time.) We owe the metalheads a debt for keeping rock alive between The Last Waltz and Soundgarden’s first A&M album. (Remember that I am an authority and you should accept this statement without thinking about it too much.)

So what about the fat metal kid? He didn’t listen to any authority figure. What does evolution say about him? I am not aware that anyone has isolated a Dokken fandom gene. If it exists, it wasn’t being passed on much 25 years ago.

When we mature, our environment requires that we think for ourselves. Otherwise we won’t prosper compared to those people who can. The free spirits with ballpoint drawings of Randy Rhoades on their jean jackets were pretty independent of the stupid social scene in high school. If they could tell that the prom was crap, maybe they could see through other more important things later in life. Maybe they didn’t invest in Enron. Maybe they know that new cars are for suckers. Maybe they know that iTunes isn’t going to save the music industry and their budget portable music players contain .wav files off the new Motörhead double live CD.