If identical twins share 100% of their DNA and siblings share about 50%, twiblings share 75%. To the best of my knowledge, twiblings don’t exist in nature.
Not among mammals, but some insects, including bees and ants, actually have 75% consanguinity (tangent, that’s a more accurate term than “shares 75% of DNA”, since the overlap in DNA is much higher, even among strangers), at least in the case of full siblings (of course it’s not the case with half siblings).
The reason for this is that these insects are “haplodiploid”, meaning that females carry two sets of chromosomes, just like e.g. mammals, but males only have one set. So while the eggs contain recombinatated (and thus varying) DNA, the father always contributes the same DNA to each of its offspring. [1/2 * 1⁄2] + [1/2 * 1] = 3⁄4, so full siblings have 75% consanguinity.
There’s a correlation between this haplodiploid condition and eusociality (as exhibited by bees and ants), though it is neither a necessary nor sufficient condition. There are at least two species of eusocial mammals, which are not haplodiploid: Humans and Naked-Molerats (interestingly, both are Euarchontoglirii, which is a fairly specific category of mammal), and many haplodiploid species are not eusocial. But it’s easy to imagine how haplodiploidhood can make the development of eusociality more likely
Humans are not eusocial. That was Edward O. Wilson being dramatic. We don’t have a biological caste distinction between reproducers and non-reproducers.
Not among mammals, but some insects, including bees and ants, actually have 75% consanguinity (tangent, that’s a more accurate term than “shares 75% of DNA”, since the overlap in DNA is much higher, even among strangers), at least in the case of full siblings (of course it’s not the case with half siblings).
The reason for this is that these insects are “haplodiploid”, meaning that females carry two sets of chromosomes, just like e.g. mammals, but males only have one set. So while the eggs contain recombinatated (and thus varying) DNA, the father always contributes the same DNA to each of its offspring. [1/2 * 1⁄2] + [1/2 * 1] = 3⁄4, so full siblings have 75% consanguinity.
There’s a correlation between this haplodiploid condition and eusociality (as exhibited by bees and ants), though it is neither a necessary nor sufficient condition. There are at least two species of eusocial mammals, which are not haplodiploid: Humans and Naked-Molerats (interestingly, both are Euarchontoglirii, which is a fairly specific category of mammal), and many haplodiploid species are not eusocial. But it’s easy to imagine how haplodiploidhood can make the development of eusociality more likely
Humans are not eusocial. That was Edward O. Wilson being dramatic. We don’t have a biological caste distinction between reproducers and non-reproducers.