Re: What percentage chimp are we?

What might be a better way to ask this question is, "What percent 
genetic homology do humans and chimpanzees share?"  What this asks is how 
much of Human DNA and Chimp DNA are identical?  Every living thing on this 
planet uses nucleic acid as it's source of coding information.  It is kind 
of like a library which gives the cell directions for making things like 
proteins and enzymes, and it tells the cell when to grow, divide, and even 
die.  The chemical structure of DNA is the same for any organism, but what 
makes one species different from another is the amount of DNA(such 
as how many chromosomes) and the sequence of each DNA molecule, or order in 
which the building blocks of DNA are arranged.  Now there are 4 nucleotides 
that make up DNA and they are A, G, T, and C.  These are put together in a 
string like fashion and the order would be represented like this for 
example:

       Human    AGTGCCGTAATTGCGTACGAGTGTUU

Now these sequences are also arranged into what is called a gene, and 
that is a portion of DNA that codes for one specific protein.  Genes 
are what we inherit from our parents, and what our offspring will 
inherit from us.  What we would look for in determining homology between 
humans and chimps is to see how many of these bases for a gene like 
hemoglobin we have in common.  So let's pretend that the top sequence is 
for a chimpanzee gene, and the one below is for the same gene in a human.

       Chimp    AGTGGCGTAATCGCGTAGGACATUU 25 bases long
       Human    AGTGCCGTAATTGCGTACGAGTTUU 25 bases long

Now, this isn't a real gene of course but the idea is the same.  If you 
look closely at the two sequences you will see that most of the bases are 
the same while a few are different.  We can figure out percent homology for 
this particular gene by seeing that humans and chimps share 20 out of 25 
bases in each gene which would be around 80%.  OK, now this is a simplified 
version of how this works because there are over 100,000 genes in humans 
and we don't even know the sequence of the entire human genome yet, let 
alone the chimp genome.  So until we actually sequence and compare the 
genome for each species we have to rely on evolutionary statistical data to 
come up with an answer for your question.

It is thought that chimps and humans branched off from each other on an 
evolution tree model about five million years ago.  Now in the scheme of 
time and evolution that is not that long ago.  So it is thought that up to 
98.4% of our genome may be identical with that of the chimpanzee.  So why 
then do we not look like chimps, and why do we have such greater mental 
abilities?  Well the answer may be not just in the percentage of bases and 
genes that we share with our chimp cousins, but where those genes may be 
located on the chromosomes as well.  

Chromosomes are large strands of DNA that are made up of thousands of 
genes, with each gene having a length anywhere from 1000 to 10,000 bases 
long.  Now over the course of time, random mutations in base sequence, and 
also a gene's position on it's chromosome can cause evolutionary change in 
an organism.  It is known that some genes are more active in some places on 
a chromosome than in others.  Kind of weird I know, but it happens. Here's 
a decent analogy.  Imagine that everywhere around the world there is only 
one type of room, with only one type of size, and one type of light switch 
placed all the way across the room from the door.  In order to turn the 
light on you have to walk through the door, across a very dark room, and 
find the switch.  Not a great place to put a switch, but it works.  The 
room is like the chromosome, and the light switch is the gene at a certain 
position on the chromosome. Now, someone comes along and says this is 
stupid, I am going to put this light switch right next to the door so that 
when I walk in it is right there.  Now this of course works better cause 
the light can be turned on faster and you don't have to feel your way 
around a dark room to do it.  In this scenario of course the decision to 
move the light switch was a conscious one whereas in evolution things like 
this occur randomly.  Imagine that is what happens to the position to the 
light switch.  In some cases it might be too high too reach, or on the 
floor, or maybe the light switch has even changed to a dimmer switch, or 
the clapper suddenly appeared with it so that you don't have to search, 
just clap!  Depending on where the switch is placed in the room it is 
easier or harder to turn on the light.    

That's how evolution works.  Changes can be drastic, or subtle, and each 
have an effect on the continuing survival of the species.  We share much of 
our genetic information with chimpanzees, but at this point we are not 
exactly sure how much.  We share even less genetic homology with things 
like squirrels, or nematodes, but it is there.  The projection for 
determining the sequence of the entire human genome is the year 2005.  I 
don't know of any attempts to sequence the chimp genome, but once we have 
the two, you'll get a more accurate answer to your question.  

Mark Sullivan