[Buttons840]

I think O is recessive (if I remember from high school correctly).

A is really AO (if we're being verbose). B is BO, AB is AB, O is OO. Each parent passes one of them on. So, a A dad and O mom would mix (being verbose again) AO and OO, and thus the child might be AO or OO, A or O.

The + or - is for an independent "Rhesus" component, as you say. Not sure how this passes through the genes. This is all like high school level knowledge, so maybe someone can share more if they want.

My dad had surgery and some paperwork we received said that he had AB blood. It became a family joke because me and my siblings are all O blood type. If my dad really did have AB blood then we are not his children. The hospital later confirmed it was a mistake.

[blendergeek]

You mostly remember correctly. One small nitpicko on the genetics (based on my high school biology)

A can be either AA or AO and B can be either BB or BO.

AB is always AB like you said and O is always OO.

[linooma_]

> I think O is recessive

Strangely, O is very common.

[thaumasiotes]

What's the strange part? "Recessive" and "common" are different concerns.

Having five fingers per hand is recessive too.

[quesera]

> Having five fingers per hand is recessive too.

Fascinating, and true.

Which engenders speculation about how the world would be different if we counted in base-12. Obvious advantages to convenient divisibility aside.

[thaumasiotes]

It wouldn't be different at all. Mostly we did use units of twelve for everything. Why do you think there are twelve inches in a foot and twelve pence in a shilling?

Asking what the historical difference would be if we wrote our numbers in base 12 instead of, variously, 10, 12, or 20 (all historically common, and 60 is prominent too), is like asking what the historical difference would be if we wrote our words in Greek letters instead of Roman letters.

Note that it was common for people to count dozens on their hands; each hand has four non-thumb fingers with three knuckles each.

[quesera]

Of course it would be different. I'm well aware of historical numbering systems, and their applications.

My point is that if base-12 was biologically natural, instead of more effortfully useful, there would be many differences in the way we do things -- although of course we would be mostly unaware of them, as a fish in water.

There would be no metric-vs-imperial units dichotomy, for example. (EDIT: Or at least the conflict would be different and likely lesser, ergo easier to switch)

NASA probably wouldn't have lost the $327MM Mars Climate Orbiter. And it wouldn't have cost $327MM in the first place.

In some cases, unit sizes would be different. That's the easy case. But in counting systems, 100 of some atomic thing would be 44% more than it is today. 1000 would be 73% more. 1MM would be almost triple. Given the attachment people have to round numbers, this would have implications. Some things would be bigger. Other things would be considered in different increments.

It's interesting. Not profound.

[thaumasiotes]

> Given the attachment people have to round numbers, this would have implications. Some things would be bigger. Other things would be considered in different increments.

No, they wouldn't. This would be a very minor effect, because the primary determinant of sizes and amounts is how big you need something to be, or how much of it you need.

Instead, you'd see the same thing we already do see: contexts in which an existing unit was difficult to work with would be given their own units of a more convenient size. Consider how horses are measured in increments of four inches, or how soft drinks are sold in unit sizes of 12 ounces, 20 ounces, and 67.6 ounces.

The units aren't called that, of course; those sizes are "one can", "one bottle", and "two liters".

[riffraff]

I seem to remember the explanation is that A and B are somewhat recent mutations in evolutionary terms, they simply have not had time to cancel out 0 yet.

Of course there's crackpot theories (aliens!) too.