Complex Numbers

Evolution, My Ass

As I pointed out in "Ain't Talkin' 'bout Love" , sometimes I get a random link that makes sense with whatever day it is.

Today is not one of those times.

Which came first, the butt or the mouth? New research gives an answer  
It's a chicken-and-the-egg question, but "which came first?" might not be the right way to think about it

Given enough time, I'd probably find a way to relate this article to today being Christmas, probably involving some pun on "ass," as in "And Mary rode Joseph's ass all the way to Bethlehem." But, as I like to say, I can't be arsed. Besides, Christmas is just another day for me, and it's always relevant to talk about assholes.

For instance, a couple of months ago, I posted another article about buttholes. It's here: "The End"  Today's article is similar, but shorter and covers a few different aspects of the digestive tract.

First, though, let me address the "chicken-and-the-egg question" mentioned in the subheading above: I don't know why this is even still in debate; eggs existed long before chickens did. I'm sure you've seen the fossilized dinosaur embryo they found recently. If not, here.  

Like many people, you may have spent hours pondering the question of which came first, the anus or the mouth?

I assure you, it keeps me up at night.

Most mammals have one major tract for solids going "in," and one for "out"; One for eating, a mouth, and another for defecation, typically considered the anus.

One of these days, maybe I'll try to find out why they start with "most." But I'm really not all that interested in searching for counterexamples.

Some scientists believe that, in evolutionary history, the mouth developed first, based on how embryos develop in the womb. Others dispute this theory, arguing that the anus developed first based on embryo development in different animals. Recently, a paper published in Nature reviewed these theories to get to the bottom of it.

These are legitimate questions because it's not like soft tissue is often preserved in the fossil record.

There's a concept in evolutionary history called Haeckel's Biogenetic Law, developed in 1866 by Ernst Haeckel. Haeckel believed that an embryo's developmental stages provide information about the adult stages of that organism's ancestors. If an embryo looks different at different stages of development, those differences correspond to how the ancestors of the species looked at adult stages.

This "law" is often expressed as "ontogeny recapitulates phylogeny," but it's not really a law and has been shown to not be the case.  

Here's the important part, though:

Researchers in the Nature study attempted to review all plausible theories by examining the blastopore, tissues, nerves and bands, and other pieces that make up the development of early human embryos. The three major theories they examined, for the evolution of mouths and anuses in bilaterians (which includes humans), were as follows:

1. The blastopore becomes the mouth, and the anus develops secondarily.
2. The blastopore becomes the anus, and the mouth develops secondarily.
3. The blastopore divides into the mouth and the anus through the fusion and separation of a tubular gut.

They found that the evidence supports the third scenario, in which the blastopore elongates and closes laterally at both ends, giving rise to the mouth and the anus simultaneously (or as simultaneous as embryonic development can get).

And maybe that explains why, with some people, it's hard to tell whether they're talking out of their mouth or out of their ass.

Anal openings first appeared around 550 million years ago, around the time of the first worm-like creatures.

That sounds like a long time, but consider: Life on Earth is probably about four billion years old, eight times longer than the time since the first asshole appeared. Granted, until about 600 million years ago, there was no multicellular life, and single-celled organisms have different means of ingestion, digestion, and excretion.

That still leaves about 50 million years between the first multicellular organism and the time when the first shit was taken. And 50 million years is certainly a long time in human terms The dinosaurs disappeared about 60 million years ago, for instance, and recognizable humans have been around for less than a million years.

So here we are, half a billion years later, surrounded by assholes.