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If two different species with different blood bases, say iron and copper, had a child together, how would that affect their child? Which blood base would the child inherit? Could they even have a child?

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If it were possible (extremely unlikely) child should have two different blood bases. – Ginden Jan 20 at 17:11

Two different species implies non-compatibility for children. There are exceptions (horse + donkey = mule) but for species so different as to have completely different blood types, I'd say "nope, not going to happen."

If you want to throw "because [insert fantasy reason here]!" at it then I'd say the kid would have the same blood as the mother on account of having to share a blood supply while in the womb.

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"share a blood supply" - I can't help but think of the different human blood-types and their incompatibility in some cases. This link showing which are incompatible and why, as well as the inheritance pattern indicates that the blood-type is inherited from both parents. A mother with 'type A' and a father with 'type B' would have a child who is 'type AB' - The mother's 'A' blood would not be compatible with the child's 'AB' blood - I can't help but wonder how this works out, can't really search on it at the moment though. – DoubleDouble Jan 20 at 17:27
@DoubleDouble: it seems it is possible, but usually not as severe as Rh factor incompatibility:… The generic name seems to be ABO incompatibility even though it applies not only to O mothers, but also to A or B mothers carrying children with B or A (respectively) or AB type blood. (…) – sumelic Jan 20 at 17:43
@DoubleDouble and others, while that's true, the asker is more referring to completely different types of blood, not A+, B-, etc. but hemoglobin vs hemocyanin – Draco18s Jan 20 at 18:03
@Mark Point. I just don't think that anything short of actual magic would suffice in this case, but I concede the argument. "Gerry, please, we're in an alien hospital, getting shot is equivalent to removing a sliver." – Draco18s Jan 20 at 19:43
Human fetuses do not "share a blood supply" with the mother while in the womb. There are two separate blood supplies, one from the mother and one generated by the fetus, and there is a structure involved that allows for nutrient transfer from one to the other, but the blood itself stays on its own side of that transfer mechanism. – Matthew Najmon Jan 21 at 5:07

Could they even have a child? No. Not in reality. At least not with out a LOT of gene manipulation and then the child would be a freak. Spock couldn't really exist (naturally).

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+1 for mentioning the obvious fictional precedent (Spock) – cobaltduck Jan 20 at 17:00
I don't know if its Canon, but "Spock's World" by Diane Duane describes the process by which Spock was designed. It took four years, and seems to have been done because the Vulcan geneticists couldn't resist the challenge. – Paul Johnson Jan 20 at 19:28
@PaulJohnson interesting. I might have to check that one out. – bowlturner Jan 20 at 19:28
Pretty sure Spock has canonically copper-based blood, so he inherited that from his father. Not sure about other half-races - only other ones I can think of are Belana Torres (Human/Klingon) and Tasha Yar's time-paradox daughter (Human/Romulan). Romulans are related to Vulcans, so she'd be likely in a similar situation to Spock. Klingons have red blood, so probably iron-based, thus more compatible with Humans. – Darrel Hoffman Jan 20 at 20:42

As stated above, it'd be impossible - but if you wanted to get really fancy, it could be an alloy of the two metals. Zinc+Copper blood bases turn into a brass based blood.

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Chemically, that doesn't really make sense. Human blood is "iron-based" not because of free metallic iron, but because of hemoglobin, an organic molecule with a single iron ion in it. Copper-based blood actually exists on Earth (e.g. in some molluscs) and uses hemocyanin, which similarly uses a pair of copper ions to bind oxygen. But it wouldn't make any sense to think of substituting Cu(x)Fe(y) into either of those molecules, nor does it really make sense to talk about an alloy existing in that context. – hobbs Jan 21 at 6:42

Assuming in your world this does work, what is the most plausible way to make this happen?

Potential issues:

  • fetal rejection from mismatched blood
  • chromosome numbers are off
  • high potential of damaged genetics
  • mixed versions are often broken

The problems that occur from blood while the child is in the womb are often from the Rh antigen marker in the blood. If the mother is negative for the antigen and the baby is positive, the mother's immune system kills the baby's blood to resolve the issue. This does not usually happen in frist pregnancy If there is no blood exchange (say because of an egg instead of a womb) or if the baby has the mother's blood (Spock's blood was green, copper based, like his father, so an issue there) then there is less issues. Why there is any issue at all is odd, as the purpose of the placenta is to make the exchanges and keep the blood separate.

Chromosome count is off, and potential damage. The system of genetics that we have has parity checks and safeguards against corruption. The y chromosome is a palindrome and can fold over on itself to repair a hole. The others all are in pairs, with one from mother and one from father. Because men have only one x chrom, an X-linked recessive disorder, while inherited from the mother, will typically affect males as they do not have the other half of the x pair to correct it. With the mixing of your beings, there will be more incomplete pairs. You might also get a weird blend causing an alien version of Klinefelter syndrome where a person has xxy.

Now about the mules mentioned earlier. Mules only work one way, horse mother and donkey father. Also, mules cannot reproduce because they are genetically broken. I dont see why you cant make a humanoid mule, but they are going to have to face certain limitations on their life which might affect their personality and perspective.

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