Leave it to the Chinese!

[Jackalope]

Uh...

Maybe I have too much practical experience with embryology. >shudder<
There are too many things that can and do go wrong with "normal" pregnancies. There's a 50-75% miscarriage rate (depending on who's numbers you look at) for pregnancies in first-world countries. That's how often the DNA gets screwed up under "good" conditions. Oh yeah, it'll just be dominant and there'll be no problems...

[LostNgone]

Uh...

Maybe I have too much practical experience with embryology. >shudder<
There are too many things that can and do go wrong with "normal" pregnancies. There's a 50-75% miscarriage rate (depending on who's numbers you look at) for pregnancies in first-world countries. That's how often the DNA gets screwed up under "good" conditions. Oh yeah, it'll just be dominant and there'll be no problems...

O come on 75% thats within the first week and a half. That number is pre-implantation. At 3 weeks that number is what 10% chance of a miscarriage?

I think those numbers are from the the same people that tell us 750,000 people die every year in the US from second hand smoke alone.

[Jackalope]

Actually 50-75% is the emergency room statistics for within the first 6 weeks.

Edit:
At least, those were the numbers they were using when I took physical anthro and population genetics. And it hadn't changed a whole lot when I took neurology maybe 5 years later. The major difference in the numbers seems to be on who does the sampling and when they take the numbers. "Silent" micarriages before 4 weeks are counted more by population geneticists, actual ER visits by epidemiologists. The rate goes way, way down after 6 weeks.

[Toawa]

It's always seemed rather amazing to me, given the fact that...

Women are (statistically, under average circumstances) only fertile maybe 20% of the time, and
~25% of sperm are killed the moment they hit the acidic vaginal environment, and
A large percentage are deformed, or are "attack" sperm which don't even try to find the egg, and
Most (95-99%?) of the sperm don't even make it to the Fallopian tubes, and
~Half of them end up choosing the wrong tube (Maybe; perhaps there are chemical markers that guide them, I don't know.), and
Odds against implantation, and
Odds of miscarriage that you just quoted,

That anyone gets pregnant at all...

[Fire Storm]

It's always seemed rather amazing to me...That anyone gets pregnant at all...

Yeah, I know. Millions of sperm go in, and in the end MAYBE one will suceed. Tiny little sperm first have to make it through a tiny little hole in the vagina (READ: The Deathtrap!), THEN they have to make it through a large cavern, and if they are lucky, they will pick the right tube.

And that's just fertilization.

[Squidflakes]

and that's natural selection at work. Only the strongest, most clever, or luckiest survive. Of course in the sperm's case, I think we can rule out clever.

[Infinity-Iz-Blue]

So, technically, if we were to, say, engineer for ourselves a wonderfully designed human-animal hybrid chances are it'll be hopelessly defecient in one way or another because it was never forced through the process of natural DNA selection?

[WhatMeWorry?]

Not necessarily. Negative traits don't always get weeded out by evolution, we got plenty of walking examples of that. Engineering people is merely a more focused and intentional method of creating humans than the more "natural" procreation. Like most things in life people tend to make it all far more complicated than it needs to be...

8)

[Squidflakes]

when refering to a human made anything, I think you can safely rule out natural selection being any part of it.