NYU scientists have traced the evolution of tomcod fish that’s been driven by pollution in the Hudson River. The NPR article is nice because it really breaks down how fish with the right genes preferentially survived the PCBs and dioxins in the river, and passed their genes on.
It also turns out that the fish “selected” for pollution tolerance end up being more sensitive to other things, like high water temperatures. It really puts, “survival of the fittest” in context. The fish are “fit” for polluted rivers, but not “fit” for warmer water.
Drosophila (fruit fly) head. Fruit flies are used extensively in biological and genetic experiments (image from Wikipedia).
Hannah Waters at Culturing Science has nice post on an experiment designed to find out how fast a population of flies could adapt to dryer conditions. Apparently, the flies could not adapt.
We tend to take it for granted that life is robust, and will adapt: “Life will find a way”. This is true to an extent, but obviously not always:
Natural selection itself is based on three assumptions in a population. The first is that there will be variation in traits, such as multiple colors of eyes or hair. The second is that these traits be heritable through the generations, that children will inherit the traits of their parents. The third is that these variable traits have differential fitness, or that some versions of a trait might help you survive better than another. Thus certain trait variants will help its carrier organism survive better, passing that trait to its offspring which will in turn bear this trait. – Waters, 2011: When adaptation doesn’t happen.
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.
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).
It starts with evidence that the mitochondria in our cells were once separate organisms and goes on to explain things like how the change from quadrupedal to bipedal, upright walking resulted in our S-shaped spine (and frequent backaches) and our unsupported intestines. It’s quite the interesting read.
In the field of cognition, the march towards continuity between human and animal has been inexorable — one misconduct case won’t make a difference. True, humanity never runs out of claims of what sets it apart, but it is a rare uniqueness claim that holds up for over a decade. This is why we don’t hear anymore that only humans make tools, imitate, think ahead, have culture, are self-aware, or adopt another’s point of view. – Frans De Waal (2010).
My students studied the question, what is life, last cycle, and through their readings and Socratic dialogue I’ve been trying to approach the question of what is sentience and what distinguishes humanity from other organisms (or robots for that matter).
We’ve found that the lines between us and them are very hard to draw.
Pushing the discussion into questions of morality, primatologist Frans De Waal has a wonderful post on where it comes from, and if there is any clear distinction between humans and other animals. He argues that morality is innate, a product of evolution, and there aren’t clear distinctions.
The full article is a worthy read, with good writing and well constructed arguments. It’s a bit too long for a Socratic Dialogue but might be of interest to the more advanced student, particularly those going through religious, coming-of-age, rites of passage, like preparations for confirmations and Bar Mitzvahs. While De Waal’s evolutionary reasoning has been used to argue against religion, he takes a much more subtle approach:
Our societies are steeped in it: everything we have accomplished over the centuries, even science, developed either hand in hand with or in opposition to religion, but never separately. It is impossible to know what morality would look like without religion. It would require a visit to a human culture that is not now and never was religious. That such cultures do not exist should give us pause. – Frans De Waal (2010).
During our last immersion, one of my students brought in the computer game, Spore. Although the game subtly indicates that it’s your progeny that gains evolutionary advances, the fact that you get to choose what you want (extra horns, poison sacks), and the fact that you can see yourself (or do I mean your creature) evolve on the screen, really smacks of Lamarckism. While it’s appealing to think, like Lamark, that you can pass on traits gained during your lifetime to your kids, despite some fascinating new research, that’s just not how evolution works.
Evolution is not directed by the organism but by their environment. In a population of organisms of any particular species there is going to be some variability due to simple, random genetic mutation. Some lucky members of the species might have a mutation that makes their muscles better at burning oxygen during sprints, making them able to run faster to get away from the lions. So they survive and pass their genes on, with their genetic mutation. Of course, if lions become extinct (disease maybe) then this trait may no longer be beneficial and something else, like maybe intelligence, would be selected for.
The game can capture your interest, however, so I’ve asked the student who brought in the game to come up with a presentation explaining why it would be useful to have the game in the classroom. I am, after all, not instinctively opposed to using computer games in class. I’m really curious to see what this game looks like from the student’s point of view.
This is a great demonstration because as you unroll the toilet paper you get a great feel for the long spans of time in the preCambrian when nothing much happens, and then, as you approach the present, events occur faster and faster. There’s 300 million years between the formation of the Moon and the formation of the Earth’s atmosphere. That’s 60 sheets! while modern man only turns up about 10,000 years ago, which is 0.002 sheets; about the width of the line drawn by a pen. Even the dinosaurs went extinct only 14 sheets from the end.
