We've all heard it.
You know you have...come on, admit it. Don't be shy.
Remember, it's the old:
"Humans and chimpanzees share 95% of the same DNA." genetobabble.
"Humans and chimpanzees share 95% of the same DNA." genetobabble.
(yawn)(reaching for Mountain Dew)
Have we really descended (sorry, that sounded too "de-evolutionary") to these depths of abysmally-absent-of-any-substantive-value arguments here in the 21st century? We have? Ooo, bummer.
Well, alrighty then, let's go to the chalkboard and re-hash the demerits of this tired-but-still-somehow-kicking assertion.
Let's start with the very basics of DNA (tip: if you don't want to wade through this stimulating discussion of biological and mathematical calculations then I will give away the prize right now---we only share about 95% similarity in less than 10% of our entire DNA sequence. I know, a big letdown, but it sure sells newspapers (just don't read the fine print or any of the dozens of caveats about the number 95%))
DNA is the language of physical life. All living creatures (Mr. Virus has been struggling to enter this club) have, at their core, a robust and incredibly complex mechanism for storing, reading, and copying the information necessary to live, grow, and reproduce. This huge encyclopedia of bio-formation is called DNA (short for DeoxyriboNucleic Acid---I know, DNA sounds more intelligent and cool, like CIA, or NSA)
DNA (99.9% of the time) is the complex arrangement of 4 very important genetic "letters" called bases. They are: adenine, guanine, thymine, and cytosine (Just remember GCAT, a nice acronym to help get you started with their names). By arranging these 4 "letters" and then using these letters to form genetic words, and phrases, and even genetic "punctuation" (some arrangements of them represent things like periods in a sentence--meaning: STOP or START new word) the cell can create amazing structures using proteins that are "Spelled out" by this genetic alphabet.
Proteins are the most important structures for life, and they are "built" by assembling anywhere from several to several hundreds of amino acids together. Think of amino acids like Legos. By "snapping together" a bunch of amino acids, you form proteins.
(Basically) there are 20 amino acids used for building proteins (20 different colors of Legos). Think about a protein like a SENTENCE. Imagine that each of these 20 amino acids is a WORD. Using these twenty different words, you can arrange them in an infinite variety of combinations (depending on how long the sentence is) to make a huge number of different proteins.
And what are WORDS made of? LETTERS. That's where GCAT (adenine, guanine, thymine, and cytosine) come in. DNA needs to use groups of these bases to point to one of the twenty different amino acids. It does this by using THREE BASES to represent (spell out) a WORD. These 3 bases are called CODONS.
An analogy will help. What is the name of the creature that meows, has claws, and usually hates dogs?
Answer: CAT. Cat is a word, that is spelled out with three letters C-A-T. Think of amino acids as words, and each amino acid is spelled out with 3 genetic letters (bases).
Here is a complete list of all twenty amino acids, and the various combination of the 3 genetic letters (bases) that spell them (code for them).
AMINO ACID (WORD) BASES (LETTERS)
ATT, ATC, ATA
|Leucine||CTT, CTC, CTA, CTG, TTA, TTG|
|Valine||GTT, GTC, GTA, GTG|
GCT, GCC, GCA, GCG
|Glycine||GGT, GGC, GGA, GGG|
|Proline||CCT, CCC, CCA, CCG|
|Threonine||ACT, ACC, ACA, ACG|
|Serine||TCT, TCC, TCA, TCG, AGT, AGC|
|Glutamic acid||GAA, GAG|
|Arginine||CGT, CGC, CGA, CGG, AGA, AGG|
Let's have some genetic fun. Let's make up a protein, let's call it: Callergin (proteins often have names that end in "in"---it makes them sound, well, proteiny). So we have our protein Callergin. Remember, proteins are like SENTENCES. Let's pretend that to make up our sentence (that we are calling Callergin) we need the words (amino acids):
Tyrosine serine threonine lysine proline (this is our genetic "sentence" that means Callergin---remember: fake, made up).
How would we SPELL that sentence (genetically speaking)??? Well, look up at the chart. To spell Tyrosine, you can spell it either as TAT or TAC. (Many amino acids can be spelled by different arrangements of these "letters"-- kind of like certain words in English can sound the same but have different spellings. Think about the word "To." There are three different ways to spell that sound: (1) To (2) Two (3) Too. All sound like the same word, but have different spellings. In the same way, there can be more than one way to spell an amino acid.)
So, getting back to spelling that genetic sentence. Well, using the chart above, it COULD BE spelled like this.
TAT TCT ACT AAA CCT.
That specific arrangement of genetic letters (in triplets called CODONS) are used to spell amino acids (WORDS) which are then grouped in long chains to form proteins (SENTENCES).
Enough of the genetic grammar lesson.
How big is the DNA in your cells?
That's a good question. The DNA in the average human being is about 3 BILLION BASES LONG. That's right, billion.
How big is 3 BILLION? Well, if you started counting from one, two, three--up to 3 billion (at the rate of one number per second) it would take you nearly 100 YEARS to reach 3 billion. I'm not joking, do the math. Divide 3 billion seconds by 31,557,600 seconds (the number of seconds in one year).
Now it's time to get down to the good stuff. Depending on what journal you read, or what forum thread you land on, proponents of molecules-to-man evolution will boast that "Scientists have compared chimpanzee DNA to human DNA, and they are (anywhere from) 95%-98.8% similar." Case closed, evolution wins, next case...right? Completely and totally wrong.
First, here's the stunning fact that you will never read in tabloids, newspapers, or hear on the talking-heads shows. In perhaps the most extensive study ever conducted comparing human and chimpanzee DNA, the researchers only compared about 20 million bases. 20 million sounds like a huge number, but when you remember that the genome is 3 BILLION bases long, their study was still less than 1% (one percent!) of the DNA.
So, the next time someone taunts you with that impressive "98%" figure, ask them: "So, what percent of the entire genome was compared?" I guarantee you that they will assume it was a 100% complete study.
Nope. Only a 1% study.
Now, if you only look at 1% of my vehicle (examine, let's say, a part of the brake pedal) you would find that it was about 98% similar to a Ferrari Testarossa, but, oops! Sorry. It's not a $200,000 custom-built foreign street-marvel capable of splitting asphalt at nearly 200mph through 12-cylinders of 5-speed, 48-valve driver joy...no, sadly, my car is a Chrysler minivan. Ouch. One turns heads, and the other, well, uh...mine can turn corners.
So much for "98% similar" in a "1% study". (I'll let you guess which vehicle represents the chimp and which represents the human)
Moving on, let's talk about other areas of the DNA that have been studied. The much touted "98%" study looked at areas of the DNA that are important for regular protein production (which only make up less than 2% of the total human DNA sequence---the other 98% or so has important functions such as gene regulation, etc.) When you study the "non-coding" portion of the DNA (some have erroneously labeled it "junk DNA") researches have found that humans and chimpanzees differ by up to 20% in some regions.
20%. Wow. That is huge. How huge? (glad you asked).
One study of the human genome found that humans share about 50% similar DNA with bananas. (No, that's not a typo, don't go back and read it again, I said BANANAS.)
So, we are 50% similar in DNA with bananas, and in many regions of our DNA, only 80% similar to chimpanzees. 50% the same as fruit...and 80% similar to a two-legged mammal. That sounds about right to me.
So what's all the fuss?!
Actually, if you look at it mathematically, we should be at least 25% similar to anything living on the earth. Why? Well, there are only 4 bases that can be in any one spot on in the genetic sequence. Pretend you are looking at the VERY FIRST letter (base) in the DNA of a snail. It has to be either G,C,A or T. Now, look at the first genetic letter of a human, it has to be either G,C,A or T. So, using the law of probability, with only four possible choices (G,C,A,T) then it should average out that we are about 25% similar to anything alive. Simple math.
So 80% similar isn't too surprising when you see that we are (physically) fairly similar, with many of the same dietary, respiratory, and circulatory needs as a chimpanzee. Looking at the math and then looking at a chimpanzee and a person, I would've guessed (before all the expensive scientific research) that we would be somewhere between 75% and 99% similar to an ape. Guess what, we are. No big surprises here.
This next one is fun, but a bit technical, but get through it, it's worth it. Our DNA is organized into groups called chromosomes (we have 23 pairs, chimps have 24). At the end of each chromosome is a cluster of repeated DNA regions called a telomere. Chimpanzees have roughly 23,000 bases of repeats. Humans are unique (among primates) with much, much shorter telomeres only 10,000 bases long.
Now, let's just assume that there is a God, and that an intelligent, powerful being actually designed life, DNA, trees, bugs, whales, chimps, and us, you and me. Wouldn't it make logical sense that the Creator would have used similar design processes for creatures who share similar structures or needs? We've all heard the phrase "Don't reinvent the wheel!" Once we have a good plan or process, why should we change it too much?
Logically inferring, based upon our observation and experience, the Creator would use similar (or even identical) aspects of life for various creatures who share similar needs/habitats/behaviours/etc. The same logical inference should be applied to DNA. It is logical that similar creatures, with similar needs, should share, if not duplicate, similar DNA.
It's time for COMPROMISE.
Alright, let's see where all this shakes down. Let's be real generous and meet with the staunch evolutionist about halfway between 80% and 98%. That would be about 89% similar.
That's 11% different. How big is 11%? Glad you asked...
Since the human genome is 3 Billion bases long (3,000,000,000) then 11% of 3 billion would be:
330 MILLION BASES DIFFERENT.
You can do a lot with 330 million...of anything. 330 million DOLLARS would go a long way to buying a small country. 330 million MILES would take you to the sun and then back and then to the sun again, with still enough frequent flier miles to do someserious sight-seeing along the way. 330 million PEOPLE is just about the population of the United States, and I don't think that anyone would doubt that these 330 million people have made a real difference in this world (actually the USA is only about 5% of the world population, but wow, what a difference 5% can make). 330 million CARS end-to-end would circle the Earth about 31 times.
A simple example to forever settle the issue.
I leave you with one final example of the power of even small differences. Compare these two small sentences:
I am really dead.
I am NOT really dead.
I am NOT really dead.
Just the tiny addition of ONE LITTLE WORD, completely and totally changed the meaning of the sentence, actually reversing/contradicting the entire meaning of the earlier sentence.
Guess what the percent different the two sentences are in terms of words? 20%.
Don't let 98% similar bother you, surely don't let 80% bother you, and please don't be upset that you share about half of your DNA with yellow fruit that bruises easily.
Come on--don't let the numbers SLIP you up.