Tag Archives: life

Evolution 101

Image courtesy of Ivica Letunic (via Wikipedia)
Image courtesy of Ivica Letunic (via Wikipedia)

A while ago I had the pleasure of being at home when some Jehovah’s Witnesses came by. After talking to them I realized to my horror that they understood evolution to mean that a chimpanzee gave birth to a fully formed modern man. I’ll probably never see them again but I’ve been wrapping my head around an easy explanation of what evolution actually is ever since and this is my attempt at an easily understandable explanation.

The simplest example I can think of is photographs. I think I have heard this comparison somewhere, but cannot for the life of me think of where. In any case; evolution is kind of like if you take a portrait photograph of a person every day from when she is born to when she dies except that every photograph represents a generation of creatures. Every generation is recognizably similar to the one before it and the one after it and yet slightly, very subtly different from both. At some points the differences between generations are bigger and change happens faster. And still, at some more or less arbitrary point we assign one generation as well as the ones after it the status of a new species just as we as a society assign, at some more or less arbitrary point, the status of a child, a teenager, an adult, a senior citizen.

Evolution, then, is not so much about individuals as it is about generations. Individuals matter, of course, but not as much as populations. The rate of mutation is generally pretty high but some 90+% of all mutations are neutral with the rest divided into beneficial and detrimental mutations. The individuals with detrimental mutations tend to die out fast, without leaving progeny, whereas the beneficial mutations spread in subsequent generations.

Mutations, though, are not the primary method of speciation for sexually reproducing life forms. Sexual reproduction uses the genetic code of two individuals to form one individual, causing that one individual to be different from both its parents even without mutations. Even siblings from the same parents vary. This then, is what forms the basis of evolution by sexual reproduction; the natural variation between individuals.

Something that always irks me is the way that nature shows present evolution as the defining moment when the cheetah catches the antilope or when she doesn’t and her cubs die of starvation. Sure, it’s that. But it’s not only that. Evolution also shows in the way that meerkats post sentries to look out for predators, in the way that buffalo form a circle around their young to protect them as well as in the way that we humans care for our weaker brethren. Evolution is survival of the fittest. But fitness in the context of evolution is not only physical fitness. We humans are absolutely useless against predators. We’re releatively small if you compare us to the bison or moose that packs of wolves routinely take down. Our teeth and claws are pathetic and we have no natural armor. And yet we are at the very top of apex predators. Intelligence plays a part, but a lone human – however intelligent – stands very little chance against everything that wants to kill us on this planet. We are social animals and evolution has made us so, giving us an advantage that forms the basis of our place on the top of the food chain.

Image via Jeremiah Blatz
Image via Jeremiah Blatz

For me, possibly the coolest thing about evolution is that even when creatures evolve into new species, they maintain their ancestral lineage and everything that entails. That means that if a pegasus ever presented anywhere, evolution would immediately go bunk. It also means that we homo sapiens are still apes, mammals, chordates and animals. And just as we are all those things, the creature on the right is what a dinosaur looks like today.

Anti-Caturday: Polly Want a Cracker

Parrot by JTrend (http://www.flickr.com/photos/jtrend/)
Parrot by JTrend (http://www.flickr.com/photos/jtrend/)

Parrots consist of nearly 400 known species in 86 genara. They are among the most intelligent birds and they are most known for their ability to mimic human speech. They have spread naturally pretty much everywhere beneath the Equator (not including Antarctis of course). Their most noticeable feature is their huge beak.

Allow me bring you back to the topic that makes me geek out about parrots; their intelligence. Some parrots have a brain-to-body size ratio that is comparable to that of higher primates. The African Grey Parrot can actually understand the meanings of words and form simple sentences on its own. The Kea parrot is especially adept at using tools and solving puzzles but all parrots are better than average birds at both.

Also; they’re very pretty.

Parrot by Danny Chapman (http://www.flickr.com/photos/11152520@N03/)
Parrot by Danny Chapman (http://www.flickr.com/photos/11152520@N03/)

Extra-terrestial life

Everyone knows how it goes in Star Trek; the intrepid team with at least Captain Kirk, a varying number of people and one guy in a red shirt go on to a new planet; the red shirt dies in some attack or another and Kirk goes off and boinks some hot alien lady. There are several things to consider about alien life however and before I go on, I’d like to recommend the talk given by Professor PZ Myers (he teaches evolutionary biology at the University of Minnesota) at this year’s TAM; A Skeptical Look at Aliens


(Part 2 , Part 3. You should also take a gander at the two slides he left out because he ran out of time)

Professor Myers makes an excellent point about how diverse life is even on this planet. How different might it be on another planet?

The Chemistry

Last year there was that whole controversy about the arsenic-loving bacteria, and while they were cool and everything, they’re not actually necessary for life outside of our own Tellus to exist. We are made, literally, out of stardust and not only that but we are also made of the most common elements in the whole universe, in roughly the relative amounts that they occur in the universe. While it seems like other planets in our solar system may not have developed life, they’re still likely to contain roughly the same elements in roughly the same quantities as Earth does. Less Oxygen of course, since it’s a by-product of photosynthesis. There are some speculations that Mars may have had life at some point before its atmosphere was blown away by solar winds. Strike that. There are some speculations that Mars may still contain life underneath the crust, hidden in the ice that may or may not be hidden there.

DNA

On Earth it would seem that DNA has only developed once. For life to evolve it is absolutely necessary for DNA or something similar to develop first. Life depends completely on a self-replicating mechanism. Evolution depends on that mechanism being flawed. Let me make it clear that I’m not saying that evolution is impossible or purely happened by chance or other such creationist nonsense. The copying mechanism itself is ever so slightly flawed in that it won’t produce the same exact copy every time. It’s like those episodes of Catch-That-Murderer type of shows (CSI, NCIS, Criminal Minds, etc) where the killer is caught by his copier or printer. The two papers look exactly the same, but the killer’s copy has a flaw that’s only noticeable when you look at it with a magnifying glass or microscope. Of course, when we get into sexual reproduction the importance of mutation becomes much less pronounced since any offspring will inevitably be a combination of both parents’ genes and so different from both.

Features

Let’s be honest; ape-like intelligent extra-terrestials seem very unlikely to say the least. As far as we know, our type of imaginative intelligence has developed only once on this planet. To compare, echo-location has apparently evolved several times, independent of each other. Eyes are also ubiquitous in this sense, having evolved several times and in several ways. Although, to be fair, we’re not nacessarily up to speed on other species intelligence either. We know that there are other self-aware at least moderately intelligent species on earth (dolphins, some molluscs, some other big apes and some birds). So who knows, there may be intelligent life on Earth as well.