57: Is Evolution Still a Theory?
Common descent will likely forever be a theory regardless of the weight of evidence mounted against it. We can thank a philosophy called methodological naturalism for this. Here methodological naturalism is explained beautifully:
I’m sure there are people thinking, “there is no evidence against common descent.” Please allow me to present but one of the countless pieces of such evidence.
Let’s consider a multimeric protein called the TCR-CD3 complex.
The TCR-CD3 complex is made up of eight separate proteins which collectively function as one cohesive unit. These proteins are; TCR a&b, CD3 delta, epsilon, gamma, and zeta.
This complex finds its function in the immune response to a pathogen. Basically when a pathogen enters your body, a cell called an APC gobbles up the pathogen, chops it into pieces, and then displays the butchered pieces on the outside of its cell membrane. The TCR-CD3 complex recognizes these pieces on the membrane of the APC, and then proceeds to release an army of molecular ninjas to bring destruction upon the Invaders.
We are going to look more closely at these different proteins which compose the TCR-CD3.
The first thing to note is that these proteins are first inserted into the membrane of a cell before they assemble together.
Here you have an individual protein embedded in the membrane, and what we will specifically focus on is the transmembrane domain (henceforth TD) which is the part of the protein that is actually in contact with the inside of the membrane, the a-helix which looks like a curly fry. All of the aformentioned proteins have this a-helix TD.
Next thing to note is that all of these proteins have a polar, or charged, amino acid in their TD. This is actually what causes them to find each other, and assemble in the proper fashion. Like magnets, blue (basic/positive) is attracted to red (acidic/negative).
The above picture is the best I could find, but it doesn’t do a great job stressing the fact that all these polar amino acids are at the exact perfect depth within the membrane relative to the proteins they’re going to bind to. Furthermore, not only must each and everyone of these 9 amino acids be in the correct location/depth, but you may not substitute one for any other type or the complex will not assemble.¹
The kicker is that you can’t rely on gradualism to slowly put these exact amino acids in the correct spot. They all have to be mutated to exactly what they are, and where they are, all in one generation!
All the components must exist simultaneously, and it’s not even necessarily an irreducible complexity issue; It’s a thermodynamic issue.
The inside of the membrane is non-polar so it is energetically unfavorable to have a polar amino acid in the TD. Shown by the chart below, polar (orange and purple) amino acids don’t exist in TDs of single proteins.
Basically the polar amino acid will be rejected by the inside of the membrane, and the protein will be ejected, and destroyed.² The way to circumvent this is to have the other proteins in the complex also be inserted into the membrane, and then bind to one another. This will bury the polar amino acids to the inside of the complex so they won’t interact with the non-polar membrane, and they will be able to stay embedded. See the red and blue are touching each other, and shielded from the membrane, whereas the single blue one has no such shielding.
Think of it like this so it’s clear why it’s ridiculously unlikely. Say you have eight pieces of string, and a giant bag filled with tons of beads, of which there are 20 different colors. Each string must have 22 beads, and you have to draw the beads at random and put them on the string. When you’re all done you must have only one red bead on six of the strings, two blues on one of the string, and one blue on another. If you have any other reds or blues in addition to those, you failed. Additionally you can’t have any blacks or greens (proline, and glycine as these destabilize a-helices). String one and two’s reds must be the exact same height as string three’s first blue, strings four and five’s reds must be the exact same height as string three’s second blue, string six and seven’s reds must be the exact same height as string eight’s blue. You have to do it all in one go. You don’t get to save anything when you got it right. The moment anything’s wrong you have to start all over again. Have fun because you’ll be playing this game for a thousand lifetimes. It is actually even more finicky than that, but hopefully the point is made well enough.
So as the science shows, this complex must have these exact specific polar amino acids in their exact specific location, and all the components must exist together simultaneously so you may not use gradualism as an explanation. This leaves you with a ridiculous probability to achieve, and we are only talking about one tiny portion of one single protein complex involved in a massive signal transduction pathway:
We can’t hardly get the right amino acids for just a single tiny part of a single complex… how are we making all those proteins above via dumb luck?
Common descent is a lie. The odds are insurmountable, and evolutionary biologists understand this very well… see the link in the beginning of the answer to understand why they refuse to be reasonable.
1.)The Organizing Principle in the Formation of the T Cell Receptor-CD3 Complex
2.)https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4515969/#!po=31.9277
Evolution: An Objective Look 