General Topics
Technical Topics
Brokerage Firms
Community Lounge
Site Support

# Evidence of evolution: Sex ratio as a function of male competition

Discussion in 'Politics' started by james_bond_3rd, Apr 11, 2007.

1. ### james_bond_3rd

The intelligent design theory claims to be scientific but has never demonstrated any ability to quantitatively predict and explain biological phenomena. Here I give you an example how the theory of evolution is crucial in understanding some of the fascinating mysteries in nature.

What is the ratio of male and female population in any species? For humans it is close to 1:1. The same approximate 1:1 ratio also holds for a large number of other species. Why? If you really think carefully about it, it doesn't make much sense from an efficient design point of view. A more efficient design should give you far fewer males. A male generally does not contribute to the reproduction process except for his sperms and he can contribute more efficiently by mating with several females.

It turns out, that the 1:1 ratio is the result of competition between the males. According to the theory of evolution, if the costs of reproduction for males and females are about the same, then competition across the entire population will lead to the 1:1 ratio.

The evolution theory also predicts that if the males compete only in a local population (within a single herd, for example) while the females disperse throughout the global population (leaving the herd at adulthood), then the percentage of males should drop significantly. The ratio is essentially a function of the local population size (Local Mate Competition Model).

It turns out, that this prediction is spetacularly confirmed by studies in parasitic wasps. See the article here:
http://www.jstor.org/view/00143820/di000260/00p01457/0
In short, the theory predicts that the percentage of sons of a mother wasp should increase with the increasing number of foundresses in a patch, with a specific formula x=(n-1)(2n-1)/n(4n-1) predicted by the evolution theory. The actual data collected from the parasitic wasps are amazingly close to the prediction.

This is just one of thousands of examples how evolution theory is confirmed in all parts of biology. The ID people of course are completely ignorant of these studies.

Challenge: Can ID people write down an equation on any biological problem?

2. ### Haroki

What a stupid premise....

3. ### infooo

LET ME GUESS haroki,

not only are you a gov paid person, debunker of 9/11

but you are into ID as well

(yup its me)

did you really think ET or you can make me go away

close to a 1 to 1, male to female ratio, is what you would certainly get if gender determination was a result of complete randomness

5. ### james_bond_3rd

Not true. Depends on how many chromosomes are needed for gender determination.

If one pair of chromosomes decides the gender (XX or XY) then the ratio is 1:1. If two pairs are needed then the ratio can be quite different than 1:1. Nature can play many tricks on this. In the most extreme case, the gender is not decided genetically but chemically at early stage of development.

Take a look at this 1996 Sciencenews item for an interesting read:
http://www.sciencenews.org/pages/sn_arch/11_16_96/bob1.htm
It talks about a strange strain of bacteria called Wolbachia.

"These microorganisms populate cells in the testes and ovaries of arthropods, often profoundly altering the reproduction of their hosts. In some species, infected males can generate offspring only if they mate with infected females. In others, infected females give birth without the need for the opposite sex. In one arthropod species, Wolbachia even transform embryos that would normally be males into females."

Virgin births, it turns out, are results of a bacteria infection...

6. ### drmarkan

Considering that men can either pass on their x or y chromosome which they have one of each, I would say the laws of probability are what bring us the 1:1 ratio.

The more times you flip a coin, the closer it comes to a 1:1 ratio. Heads=x chromosome, tails=y chromosome. Very simple and does not bring anything to the table in regards to the debate between evolution vs. intelligent design debate.

7. ### james_bond_3rd

Read my post above. This is only true if the gender is decided by two chromosomes, either X or Y.

Nature is more complex than this. In many species, the gender is decided by three chromosomes or more. There is a Paternal-Sex-Ratio chromosome (a B chromosome) whose sole purpose (as far as we know today) is to distort the sex ratio of the offsprings. In other species, the gender is decided chemically after birth, rather than genetically. So the ratio can vary wildly from species to species.

8. ### fhl

This really is rather easy.

God established that one man should marry one woman, as told in Mathew 19 and Mark 10. Do you need to be a scientist to figure out why there is a one to one birth ratio?

9. ### james_bond_3rd

What did God say about insects?

10. ### pattersbGuest

this conclusion starts with the assumption that a Designer is interested in "efficiency", if anything this is actually more evidence of a designer.

If a 1-1 ratio is NOT, biologically speaking, optimal, evolution and/or natural-selection would have weeded us worthless men out a long time ago....

#10     Apr 12, 2007
ET IS FREE BECAUSE OF THE FINANCIAL SUPPORT FROM THESE COMPANIES: