6 ms·

Apologies for the low-effort comment, but this really freaks me out. I had no idea birds could reproduce asexually! That's crazy! Feels like an unanswerable qu

Apologies for the low-effort comment, but this really freaks me out. I had no idea birds could reproduce asexually! That's crazy! Feels like an unanswerable question, but: could we ever see something like this in mammals? A virgin birth, for lack of a better phrase?

MisterTea 5y ago
It's been proposed that artificial sperm could be fashioned from a woman's DNA. I suppose a child born from both a mothers egg and "sperm" could be considered a self made clone.
simiones 5y ago
According to wikipedia, it does occasionally happen that a human egg cell undergoes parthenogenesis and starts developing, but as far as has been recorded, the fetus is never viable and is usually regarded as a type of tumor called a teratoma; occasionally, this does lead to some fetus-like shape of the tumor, in which case it is known as a fetiform teratoma. Interestingly, there are a handful of cases of functioning human individuals who have cell lines in their body that are the result of parthenogenesis: an egg cell starts dividing by itself, and is fertilized only after this process has started. Next, the feritilized cell line develops normally, while the unfertilized cell line keeps developing as well but in limited ways - in the first known case, the white blood cells of a boy were found to be entirely derived from his mother, while other cell lines were normal XY cells inherited from both parents. https://en.wikipedia.org/wiki/Parthenogenesis#Humans https://en.wikipedia.org/wiki/Parthenogenesis#Humans
- simiones 5y ago
  Also found a medical article describing a clinical case and also making the parthenogenesis link. Caution when clicking, the article also contains some photos of the teratoma, which are slightly disturbing! https://meridian.allenpress.com/aplm/article/130/10/1552/459697/Fetiform-Teratoma-Homunculus https://meridian.allenpress.com/aplm/article/130/10/1552/459...
dnautics 5y ago
> could we ever "ever" is pretty open-ended. In principle, it's possible. The most obvious problem is that if the maternal genes include any that are homozygous lethal or homozygous impaired, the embryo is also a no-go. This is in principle fixable using genetic editing using known techniques. The more subtle biggest obstacles that I can think of of the top of my head is DNA methylation-related defects. If you are interested in a "quick soundbite example" of why this is important, I recommend reading https://en.wikipedia.org/wiki/Prader%E2%80%93Willi_syndrome https://en.wikipedia.org/wiki/Prader%E2%80%93Willi_syndrome (note the 25% of cases when this is what happens when there are by bad luck two maternal copies - and zero paternal copies - of ONE chromosome, similarly Angelman's syndrome); all chromosomes -- or any other chromosome, it appears -- is embryonic lethal in humans. The underlying mechanism is: https://en.wikipedia.org/wiki/Genomic_imprinting https://en.wikipedia.org/wiki/Genomic_imprinting There is not any known way to effectively edit DNA methylation. It doesn't take star-trek level phlebotonium to get there (it's physically possible, just not with current levels of tech).
pippy 5y ago
There's a great passage about this in Genome by Matt Ridley, which is a great book for anyone interested. In mammals both the male and female gametes imprint their DNA in their sex cells to repress certain genes, if you combine two generic sequences from two males (with no modification) the zygote forms with no brain and too much placenta and dies soon after. If you do the reverse with females, you wind up with a oversized head and no placenta. The working theory is embryonic development is a competitive environment, where males want the best for their offspring at the expense of the female host, and the females 'fight' back by limiting the amount of resources the child has. it's only been recently we've had the technology to remove the epigenetic markers from DNA sequences to allow combinations of same sex strands.
thaumasiotes 5y ago
> Feels like an unanswerable question, but: could we ever see something like this in mammals? A virgin birth, for lack of a better phrase? The question is easy to answer. Yes, this is a development that shows up from time to time. Species displaying only asexual reproduction all tend to be evolutionarily young, which implies that adopting the strategy rapidly leads to extinction, but it has short-term benefits which mean that there's usually something around trying it out. (And then there are species with obligatory parthenogenesis and also obligatory sexual reproduction, like aphids, which don't experience the problems that pure-cloning species do.) By way of examples of sexually-reproducing species shifting to parthenogenesis, there is a species of lizard that can only reproduce that way. We can be certain they originally reproduced sexually since they still engage in a (pointless) simulation of copulation.
- dvsfish 5y ago
  Wow! Do you know what the lizard species is called? I would love to read more on that.
  - seryoiupfurds 5y ago
    https://en.wikipedia.org/wiki/New_Mexico_whiptail https://en.wikipedia.org/wiki/New_Mexico_whiptail

MisterTea 5y ago

It's been proposed that artificial sperm could be fashioned from a woman's DNA. I suppose a child born from both a mothers egg and "sperm" could be considered a self made clone.

simiones 5y ago

According to wikipedia, it does occasionally happen that a human egg cell undergoes parthenogenesis and starts developing, but as far as has been recorded, the fetus is never viable and is usually regarded as a type of tumor called a teratoma; occasionally, this does lead to some fetus-like shape of the tumor, in which case it is known as a fetiform teratoma. Interestingly, there are a handful of cases of functioning human individuals who have cell lines in their body that are the result of parthenogenesis: an egg cell starts dividing by itself, and is fertilized only after this process has started. Next, the feritilized cell line develops normally, while the unfertilized cell line keeps developing as well but in limited ways - in the first known case, the white blood cells of a boy were found to be entirely derived from his mother, while other cell lines were normal XY cells inherited from both parents. https://en.wikipedia.org/wiki/Parthenogenesis#Humans https://en.wikipedia.org/wiki/Parthenogenesis#Humans

simiones 5y ago
Also found a medical article describing a clinical case and also making the parthenogenesis link. Caution when clicking, the article also contains some photos of the teratoma, which are slightly disturbing! https://meridian.allenpress.com/aplm/article/130/10/1552/459697/Fetiform-Teratoma-Homunculus https://meridian.allenpress.com/aplm/article/130/10/1552/459...

dnautics 5y ago

> could we ever "ever" is pretty open-ended. In principle, it's possible. The most obvious problem is that if the maternal genes include any that are homozygous lethal or homozygous impaired, the embryo is also a no-go. This is in principle fixable using genetic editing using known techniques. The more subtle biggest obstacles that I can think of of the top of my head is DNA methylation-related defects. If you are interested in a "quick soundbite example" of why this is important, I recommend reading https://en.wikipedia.org/wiki/Prader%E2%80%93Willi_syndrome https://en.wikipedia.org/wiki/Prader%E2%80%93Willi_syndrome (note the 25% of cases when this is what happens when there are by bad luck two maternal copies - and zero paternal copies - of ONE chromosome, similarly Angelman's syndrome); all chromosomes -- or any other chromosome, it appears -- is embryonic lethal in humans. The underlying mechanism is: https://en.wikipedia.org/wiki/Genomic_imprinting https://en.wikipedia.org/wiki/Genomic_imprinting There is not any known way to effectively edit DNA methylation. It doesn't take star-trek level phlebotonium to get there (it's physically possible, just not with current levels of tech).

pippy 5y ago

There's a great passage about this in Genome by Matt Ridley, which is a great book for anyone interested. In mammals both the male and female gametes imprint their DNA in their sex cells to repress certain genes, if you combine two generic sequences from two males (with no modification) the zygote forms with no brain and too much placenta and dies soon after. If you do the reverse with females, you wind up with a oversized head and no placenta. The working theory is embryonic development is a competitive environment, where males want the best for their offspring at the expense of the female host, and the females 'fight' back by limiting the amount of resources the child has. it's only been recently we've had the technology to remove the epigenetic markers from DNA sequences to allow combinations of same sex strands.

thaumasiotes 5y ago

> Feels like an unanswerable question, but: could we ever see something like this in mammals? A virgin birth, for lack of a better phrase? The question is easy to answer. Yes, this is a development that shows up from time to time. Species displaying only asexual reproduction all tend to be evolutionarily young, which implies that adopting the strategy rapidly leads to extinction, but it has short-term benefits which mean that there's usually something around trying it out. (And then there are species with obligatory parthenogenesis and also obligatory sexual reproduction, like aphids, which don't experience the problems that pure-cloning species do.) By way of examples of sexually-reproducing species shifting to parthenogenesis, there is a species of lizard that can only reproduce that way. We can be certain they originally reproduced sexually since they still engage in a (pointless) simulation of copulation.

dvsfish 5y ago
Wow! Do you know what the lizard species is called? I would love to read more on that.
- seryoiupfurds 5y ago
  https://en.wikipedia.org/wiki/New_Mexico_whiptail https://en.wikipedia.org/wiki/New_Mexico_whiptail