# Reproduction without mating



## Brian G Turner (Jun 3, 2015)

It appears that a wider range of animals may be able to spawn without sexual reproduction than previously thought:
http://www.bbc.co.uk/news/science-environment-32958033

What would be really interesting to know is which groups of animals this has been observed to apply to - presumably it's not been seen in mammals?


----------



## Ray McCarthy (Jun 3, 2015)

Komodo Dragons do it some times.
There is a Whip Tail Lizard in New Mexico (or maybe Arizona?) that ONLY has females.
https://en.wikipedia.org/wiki/Parthenogenesis

I researched this extensively for my Talent Trilogy SF, as my Earth protagonist was warned that being a female Healing Mage, she needed to take care, even though no other people from Earth within 80,000 light  years. Such a child would NOT be an identical twin to the mother as the two mothers' Mitochondrial DNA is different. This is one reason why many generations of mammoths from an initial Elephant mother are needed to get "proper" mammoths.

Clones do not always be identical like Identical Twins.

No natural cases in mammals, but laboratory attempts with mice I think ...

Of course it's now possible to have a fertilised human egg using DNA from a 2nd female rather than a man. 
There was an SF novel were something that escaped from a lab wiped out men.


----------



## chrispenycate (Jun 3, 2015)

There have been certified cases of parthenogenetic reproduction in humans, but extremely rare (So don't go considering her ways yet). So mammals, but exceedingly uncommonly.


----------



## Ray McCarthy (Jun 3, 2015)

chrispenycate said:


> certified cases of parthenogenetic reproduction in humans


Really?
Any references?


----------



## Mirannan (Jun 3, 2015)

Ray McCarthy said:


> Really?
> Any references?



I can only think of one reported case in humans, and that report is 2000 years old and hardly scientific.

Incidentally, although parthenogenesis is very difficult and probably currently impossible, virgin birth isn't even difficult. If one is being legalistic about the definition of virginity, that is,


----------



## Ray McCarthy (Jun 3, 2015)

Mirannan said:


> I can only think of one reported case in humans, and that report is 2000 years old and hardly scientific.


Also even if true might not be parthenogenesis anyway. Technically virgin birth is a separate category.

I remember a discussion in college between some more rural lads as to the definition of when a heifer became a cow, and if it made a difference if a bull or AI was involved.

I was surprised too that sex chromosomes can be completely different systems in different species, which explains why mammal and many reptile  parthenogenesis can only give a female and birds parthenogenesis results in a male.
See

XY sex-determination system
ZW sex-determination system
X0 sex-determination system
Also related
https://en.wikipedia.org/wiki/Haldane's_rule

There is a strong theory that any likely alien life of advanced nature would have four limbs, head at one end and two person sex. But certainly the sex chromosomes would be different system and also amino acids and vitamins would be different. We might find no vitamin C on their world (most animals here don't need it, but oddly cavies do) and there might no plant or animal here that provides some equivalent of vitamins or amino acids they need.

Science is fascinating.

It's interesting why Mules (stallion vs donkey) are more common than Jennys (Mare vs donkey) apart from economic value. Mares are fussier than Stallions. Interesting to that a Jenny unlike a Mule isn't always sterile.


----------



## Stephen Palmer (Jun 4, 2015)

'Science is fascinating' - sez it all!


----------



## Mirannan (Jun 4, 2015)

Ray - Head at one end and two person sex, maybe. However, I can easily imagine trinary sexual patterns (in which one of the sexes is basically an incubator or supplies some essential compound or both) and body plans other than two arms/two legs are even easier. Centauroid forms for example, or the body plan of the Moties, or that of Niven's fithp.

Also, sex chromosomes aren't necessarily the only plan either. Sex in crocodiles is determined by incubation temperature, IIRC. And finally, plasticity of sex is not only believable, but fairly common - although admittedly only in fish, again IIRC.


----------



## chrispenycate (Jun 4, 2015)

Ray McCarthy said:


> Really?
> Any references?


I can't find them - it was about forty years ago, and I was in a library with books - I hadn't any access to the Web back then, if it even existed. Note, I said 'certified' not proved - and there are plenty of uncertified cases, as one could imagine. If I remember correctly, the offspring - all female, obviously - were haploid, so hardly constituted a viable population - and it's a vanishingly low number, anyway. However, I have discovered that in turkeys it's reasonably common. Now, where can I use that fact?


----------



## Ray McCarthy (Jun 4, 2015)

chrispenycate said:


> turkeys it's reasonably common.


I for one welcome our new alien overlords that have outlawed Thanksgiving and Christmas.




Mirannan said:


> However, I can easily imagine trinary sexual patterns


Yes, but what evolutionary advantage?
The more complex it is the less likely to happen. Of course perhaps it's advanced genetic engineering for an economic advantage. It's not true about KFC though. I suspect the word "Fried" is why they changed name.



Mirannan said:


> Centauroid forms for example


We can imagine hexapod like cattle too. Or Moties. But Biologists seem to think it's unlikely for more "advanced" organisims as explanation as to why no mammals, reptiles or marsupials or birds with more than four limbs. Bilateral symmetrical seems to be argued too, so the Moties seem unlikely.
There is a difference between what seems plausible in SF, what's technically or hypothetically possible and what Biologists think is plausible. 
But we have a sample of ONE! We need to figure a way to explore 10,000 planets teaming with life!



Mirannan said:


> plasticity of sex


Greenfly
also the freshly born ones can be pregnant.


----------



## Mirannan (Jun 5, 2015)

Hmmm... Just as an example. centauroid forms might well have a distinct advantage in a plus-gravity field. I'm not sure whether anyone has done any biomechanical simulations based on a 1.5 or 2G field; if not, maybe someone should?


----------



## hardsciencefanagain (Jun 5, 2015)

there are slight indications(e.g.depending on how you view their phylogeny*)that ecology MAY be a driving factor in varanid lizards
in some cases "unisexuals " vastly outnumber syntopic bisexual species,particularly in more humid habitats.
*The effects of gene introgression have yet to be sorted out of allozymic phylogenetic trees.
The number of shared alleles (result of _mt_DNA analysis)point to hybrid origins of unisexuals.

phasmids are parthenogenetic,_Xenopus_(i think)


----------



## Ray McCarthy (Jun 7, 2015)

@Mirannan 
James White (Federation World and Sector General series) has very imaginative aliens. I like his stuff. Unless we get to have FTL drive and explore, we won't know if reality is closer to boring Biologists or funky James White.


----------

