Well, call me Captain Obvious

From humans to black-tailed prairie dogs, female mammals often outlive males – but for birds, the reverse is true.

Now researchers say they have cracked the mystery, revealing that having two copies of the same sex chromosome is associated with having a longer lifespan, suggesting the second copy offers a protective effect.

Err, yes?

X,X and X,Y are fairly normal among humans. X,X,Y, and X,Y,Y happen and so on. X,O does too – but O,Y never does.

Further, it’s long been assumed – ‘cuz even I’ve read about it – that if there’s some buggery on one X then the other can take over and correct it, something that can’t happen with the Y, for the same reason that O,Y can’t happen. And I’m alo why no one even speculates about the possible existence of Y,Y.

13 thoughts on “Well, call me Captain Obvious”

  1. “revealing that having two copies of the same sex chromosome”

    except they aren’t copies…. one;s from your ma and one’s from your da.

  2. The Pedant-General

    Which is why (see what I did there? ) you are very very very unlikely to have YY – you would need a Y from your Ma.

  3. As a (retired) physicist, I am completely unqualified to answer, however I’ll have a go…
    It appears that in order to produce a zygote one needs an egg, which is, as far as I’m aware, always X and another sex chromosome from somewhere else. Hence every variation of sex chromosome mixture must have an X in there somewhere. Unless someone can invent a way to create a viable zygote from two sperm, you ain’t gonna get YY or OY (not even in the Jewish community).

  4. Ben Schapiro observed, while discussing the Bruce currently known as Caitlyn Jenner, that every cell in his body contains a Y chromosome, with the ironic exception of some of his sperm cells.

  5. For those who aren’t aware already, the sex chromosomes in birds are designated Z and W, with males being ZZ and females ZW. This is how cuckoos produce eggs that mimic (to sufficient accuracy) those of their different host species. The genes controlling this are on the W chromosome, so a female born in a reed warbler’s nest can only parasitise reed warblers, whereas a male cuckoo can mate with any female. Hence the females exist as separate subspecies, each with a different host, while there’s only one ‘species’ of male cuckoo.

    Explained at greater length in some of Richard Dawkins’s books.

  6. ‘… female mammals often outlive males…’

    Human males historically do the most hazardous, arduous labour and wear out quicker.

    Animal males are often killed fighting over mating rights, females of course are not. Older males lose out to the youngun’ sooner or later. In some species males are solitary so must hunt alone and do not therefore enjoy collective hunting benefits, unlike females who are in packs. Also if a herd is attacked the males tend to lead the defence and therefore more likely to be maimed (death sentence) or killed outright.

    Birds: females do most of the nesting duty sitting on the eggs and therefore being stationary, more vulnerable to predators particularly if ground nesting species.

    I wonder if any of the above has any bearing on the longevity of males v females?

  7. @Hallowed Be

    “except they aren’t copies…. one;s from your ma and one’s from your da”

    Well said. If not, every female would be a clone of mother – Guardian: always wrong

    @Chris

    Thought I had it until “a female born in a reed warbler’s nest can only parasitise reed warblers”

    Are you saying female cuckoos mate with the male “husband” of nest couple, then lays her egg(s) in their nest?

    @John B

    Agree

    Lions let the lioness hunt, but if they fail the lion steps in and does the job
    https://www.youtube.com/watch?v=dpvLj_OB-Y0

  8. “Our study suggests that the unguarded X is an underlying genetic factor that can influence lifespan, but many external factors can influence longevity in different ways such as predation, risky behaviours, establishing territories and access to quality nutrition,”

    Besides that…. And what the Grauniad makes of it for a Headline,,, And getting it completely wrong….

    Some smart Cookies added another factor to “why don’t I live forever” …..

    The original article is …Good.. And it does show a …Connection.

    What I’m truly surprised about is that they missed ( or ignored ) the obvious conclusion of the data presented in the actual article. There’s……
    Silly/real version: if the one table is real, it’s going to be textbook material. it’s beautiful, and on a macro scale explains a lot.

  9. Other reason, in mammals, the X chromosome contains some genes necessary for survival, the Y does not. The Y purely holds genes necessary for maleness. So an egg fertilized with a defective or missing X chromosome cannot survive as it is missing certain key functions.

    One reason that more male fetuses spontaneously abort and why some genetic diseases are male dominated – because the genetic defect is on the X and men only (mostly) have 1 such and therefore cannot recover the functionality if lost.

    BTW, there’s also XXXY and XXYY I believe, not sure how viable but I think examples have been found. XXY is relatively common and can be inherited apparently. By Relatively I mean there are extant examples and not just the odd rarity, actually it is well under 1%, and under 0.01% I think.

  10. @Pcar
    That’s my not being very clear, sorry. A female cuckoo born in a reed warbler’s nest will be the daughter of a female that lays eggs resembling those of a reed warbler (much bigger, but reed warblers don’t seem to notice that). She will inherit those genes from her mum’s Z chromosome, so will lay similarly patterned eggs, which will only ‘work’ on reed warblers. A male cuckoo has no Z chromosome, and so can mate with any female without influencing the patterning on the eggs she lays.

    There are currently three different bird species that can be parasitised by British cuckoos, but Dawkins hypothesises that there have been other species in the past who evolved to identify the cuckoo’s egg and so are no longer ‘victims’. He explains all this much better than I do, which is why he’s paid the big bucks :).

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