Got an interesting email this weekend. From someone who really knows how to be tactful.

Basically, Rebecca asked, "What is so common about humans with 48 chromosomes?"

An extremely polite way of saying, "Hey, dummy. You screwed up. The normal human DNA complement is compressed into 46 chromosomes, not 48."

And she's right. I'm usually pretty good with numbers, but I have always had trouble with this one.

Is it 23 pairs plus the sex chromosomes, or 23 pairs including the sex chromosomes?

Well, it's 23 pairs which include the sex chromosomes. If you want to know what the 23 pairs look like, check out the National Health Museum's diagrams.

So, any human with 48 chromosomes would be remarkable, indeed.

She also gave me the technical name for the condition where an individual receives three sex chromosomes (usually XYY) instead of the usual two...trisomy. Making the 47 chromosome humans fairly rare birds.

Thanks, Rebecca.

Which brings up an interesting topic that I've been meaning to discuss, but I don't think I ever mentioned here.

I always thought sex was sex, as in being fairly universal within all living things. Turns out it's not.

If a mammal gets the XX sex chromosomes, it is female. If it receives one X (required) and the diminutive, parasitic Y chromosome, the mammal becomes a male.

But it is not that way with other forms of life.

First off, bird sex is determined by a completely different set of chromosomes. And the individuals with matching sex chromosomes come out male. With avians, it is the females which have mismatched sex chromosomes.

For many (if not most?) reptiles, sex is determined by environmental factors, not simply the complement of chromosomes. And with some species, sex can change during the life of an individual. I think I've known that since I was a little kid catching and raising horny toads, but it wasn't until surprisingly late in life that I learned that the herps were so different from us.

Which adds credence to so many scifi plots. And makes you wonder why so many nonterrestrial species in Star Trek had standard male/female sexes.

Otherwise, a busy but boring day. Writing comments on three major projects proposed by our federal land management agency. All designed to kill sagebrush to make more grass for cows (but all written with other, more environmentally sound justifications).

Absolute final deadline for comments on their EAs was today. Would have done a better job of meeting that deadline is the damn phone would have quit ringing.

Two of them were calls from the boss, wondering where my work was.

Well, if I wasn't wasting 15-30 minutes with each of your calls, a hunter call, the federal biologist's call, one of my neighboring biologist's two calls (on these same sagebrush projects) and one of my game wardens wanting to know how old his bull elk was last fall and was there anything older taken, I would have had these things done two hours sooner.

But they're gone now, on someone else's desk.

Weather permitting, it's lek surveys in the morning.