^though that brings up a good point, I have to question that. Has there ever been an instance where a bird has birthed another type of creature? I mean, no matter how 'slow' evolution is, shouldnt we see some sort of change in creatures? How have we not evolved at all in the past...i dunno, 1000's of years? not even an extra finger or a extra toe or a extra hand?

 

Am I the only one that saw "The Story of Man?"

 

Um, do you mean why hasn't a bird given birth to a dog? Or do you mean, why hasn't a bird given birth to a bird that is different enough to be a separate species?

There are mechanisms in place that ensure you do NOT grow extra fingers or toes. There are thousands of regulatory proteins which function solely to make sure that you do not stray from the path. In order for an extra toe to form, there has to be a special sequence of events due to changes in the genome that allow for NORMAL development in other areas, yet extra growth in one specific area. To simply mess around with genes is far too dangerous and costly, for the sake of an extra toe...

The only place where genes are actively rearranged, besides in your gametes, is in the final lineage of your hematopoeietic stem cells which derive the cells for your immune system. B and T cells undergo somatic hyper-mutation as well as isotype switching by the rearrangement of gene segments in order to produce the millions upon millions of different T/B cells which grant you acquired immunity to all the millions of antigens presented to your body.

For all other cells, straying from the path would have disastrous consequences (if you were even born). Development is not simply division and separation, there are cell events which are signaled to occur and then turned off after developmental stages are complete. We know but a fraction of a fraction of a percent of the signals being sent from the moment of conception to the moment of your death.

To put it simply, even the smallest changes can produce atrocious outcomes. It is not like you can change a base pair here and then you will have an extra toe. If you fiddle around you may upset the flux of chemicals and signals on a regular routine, and in the simplest of cases, find yourself with cancer. If you mess around during development, there is no guarantee you will be born. There are many groups of genes which are "protected" as they have been passed down from some of the earliest ancestors, and you may have a dozen different signals or checkpoints that must be passed before a single gene can be turned on. This type of regulation is evident everywhere.

If you're looking for a good example of genetic changes which result in positive or negative outcomes, take a look at sickle cell and malaria. Sickle cell results from a mutation in your red blood cells which prevents proper oxygen binding to hemoglobin, thus the cells have a sickle shape. It is a change in ONE BASE PAIR (an adenine to a thymine) and so on two subunuts of the hemoglobin protein, you have 2 amino acids which are wrong; in other words, 2 out of 500+ amino acids are wrong. If you are homozygous for sickle cell, you have a very tough time staying alive. However, the malarial parasite, which relies on red blood cells, is incapable of utilizing sickle RBCs. And so, if you are a carrier (heterozygous) for sickle cell, you are actually granted "immunity" or a selective advantage over your neighbors who may be homozygous for sickle cell, or completely normal:

While the homozygous sickle cell individual has a hard time staying alive, and the normal person suffers from malaria with their healthy RBCs, a heterozygous carrier would be able to both live (so long as they are not running marathons) with sickle cell as well as ward off malarial infection (due to the fact that there are fewer RBC for the parasite to infect).

There you have an example of a genetic mutation which, in some circumstances, proves beneficial. What's more interesting is that sickle cell is predominant in the African community; guess where malaria is also dominant?

In terms of biology, genetics is not everything. Genetics is the potential of an organism, but there is no guarantee you will reach that potential should you clash with your environment. And if you're looking for drastic changes, stay alive for a few more decades, and you'll see what our environment is doing to us

 

How come there are different breeds of dogs?

Race is nothing more than breed, just not politically correct. People are not comfortable thinking that we are just another animal so came up with the word "race". Dogs, who are the Canis lupus species, have generally smart breeds like the border collie, and generally stupid breeds like the afghan hound. Breeds of dogs also differ in their physical traits.

People, who are the Homo sapiens species, share that same general differences among their "races", but no scientist is willing to stick their neck out to quantify them.

 

[QUOTE=ikeyballz,Oct 19 2009, 02:45 AM] How have we not evolved at all in the past...i dunno, 1000's of years?

 

We DO have people with extra fingers and toes. The average rate of occurrence is 0.2%.
http://en.wikipedia.org/wiki/Polydactyly

Also, there are about 50 human generations per 1000 years. (Assuming 20 year generations.) A research scientist had to watch e.coli for 20,000 generations, over the period of 20 years, before seeing a noticeable advantageous mutation - in other words, evolution. In humans, that would be 400,000 years, longer than modern humans are presumed to have been around. So it's no surprise we haven't seen "evolution" on historic time scales (a few thousand years.)

 

OT:
[media]http://www.youtube.com/watch?v=gppcC9sLMI4 [/media]

 

^^Awesome commercial
[media]http://www.youtube.com/watch?v=-h3dtweyAwg [/media]&feature=related

 

So now every time a black person calls me racist I can just say "I have no problems with humans what-so-ever! Some of my best friends are human!"

 

Chinese, Japanese, and Dutch are not races; they're nationalities.

African is not a race; it's a continentality.