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Is it? I always thought that species is defined as a group that can have fertile offspring. Horse and donkey, for example are not the same species because thei

Is it? I always thought that species is defined as a group that can have fertile offspring. Horse and donkey, for example are not the same species because their offspring, a mule, is not fertile.

maxerickson 5y ago
You get the occasional fertile mule!
- tomca32 5y ago
  Oh interesting. I had no idea
  - tsimionescu 5y ago
    Theoretically that wouldn't be a killer issue, since fertile mules are extremely rare, so you could refine the definition to say "is very very likely to produce fertile offspring" (while horses and donkeys breeding is not). The bigger problem are things that have massive morphological differences but can still successfully interbreed, such as dogs, coyotes and wolves. They produce fertile hybrids and there is good evidence that this occasionally happens in the wild, but nevertheless it is rare and they have clear, stable morphological distinctions, even in areas where they overlap. Even worse, that definition is entirely useless for paleontology, as it is impossible to know if two individuals species could even interbreed, nevermind knowing if their offspring would be fertile. Even modern genetic evidence (which is extremely rare for fossils anyway) is very open to interpretation on the matter of potential interbreeding ("Neanderthal" genes in modern humans could more or less as easily be common genes older than both H. Sapiens and Neanderthals - we have far too little evidence to be sure, and no chance of genetic material from an older ancestor).
    - AlotOfReading 5y ago
      If neanderthal or denisovan genes were ancestral, you would be able to find them broadly in African genomes and some of them wouldn't carry adaptations to environments not found in Africa. Instead they reinforce (and inform) our understanding of early human populations out of Africa.
retrac 5y ago
It breaks down with edge cases. There are a few documented "ring species" such as a diverse land-based amphibian around a lake. At all points the adjacent neighbours can mate, but if you take examples from the far side of the lake, they cannot. One species? Two? Infinite? I think it was Richard Dawkins who extended this idea through time. We could mate (sorry) with our immediate ancestors, who could with theirs, etc. and in fact there's a continual chain like that all the way to any other mammal. When did we stop being our ancestral species and become H. Sapiens? No clear line.
- lazide 5y ago
  It’s the ‘what’s a sandwich’ problem, which is hard. Is a stack of pancakes a sandwich? Is a stuffed pita a sandwich? What is it that makes a PB&J clearly a sandwich, and excludes a stack of pancakes with butter in between - and doesn’t exclude a club sandwich.
  - jjk166 5y ago
    If you eat two pancakes with butter between like a sandwich, it is a variant of butter sandwich. If you cut up your PB&J such that you're only eating pieces of bread with some spread on them, that is not a sandwich. The bread must act as a container for the contents during consumption, regardless of ingredients. More generally, the key delimiter for sandwiches is the aspect ratio of the individual items contained by the bread. For something to be a sandwich, all of the major items inside must have one dimension which is substantially smaller than the other two. Sliced meats, bacon strips, cheese slices, sliced vegetables, lettuce leafs, spreads, patties, etc are all valid. Thinly spread peanut butter and jelly between bread is a sandwich, but a bread bowl with a pool of jelly and peanut butter where the depth is comparable to the radius would not be a PB&J sandwich. Flat cheese slice between bread is a sandwich, mozzarella sticks are not sandwiches. Hot dogs are by default not a sandwich, but if you cut the hot dog into thin strips it becomes a sandwich. An oreo is a sandwich but a quadruple stuffed oreo is not. The only commonly accepted sandwich which this definition claims to be a pseudosandwich is the meatball sub.
    - 5y ago
inglor_cz 5y ago
Even if we limited ourselves to the Homo genus, the rule does not work well. Based on the admixtures of Neanderthal and Denisovan DNA in modern humans, we once had a lot of sex with those other humans (and they with us), resulting in fertile offspring, but the differences between us and them are pretty meaningful and probably worthy of not considering us and them just subspecies of the same species. For example, Neanderthals probably could not vocalize in the same way that we do; and being capable of speaking is quite an important distinction. They had very different anatomy, including that of important joints (shoulders).
Scarblac 5y ago
There are far too many edge cases (e.g. ring species), but it's also not practical. How are you going to decide whether two individuals can't reproduce together, or choose not to? What if all you have are some dead specimens? It's mostly based on DNA analysis these days, I think.
Dylan16807 5y ago
I think the fertile offspring test would say a lot of these humanoids aren't different species, though?
- FundementalBrit 5y ago
  Is the domestic dog the same species as the coyote or wolf? All can interbreed all can have fertile offspring with each other. Then look at the genetic variation between all three species. Yeah this type of science is the stuff which destroys careers...
sdenton4 5y ago
How do you actually test that as a working ecologist, though? Given two geographically and somewhat morphologically district warblers (for example) you would need to convince two of them to breed (after capturing at least one) and then check viability of an offspring. It's not terribly practical... Or, in this case with ancient human remains, there's no way to check viability when all subjects have been dead for a hundred thousand years.

Is it? I always thought that species is defined as a group that can have fertile offspring. Horse and donkey, for example are not the same species because their offspring, a mule, is not fertile.

maxerickson 5y ago

You get the occasional fertile mule!

tomca32 5y ago
Oh interesting. I had no idea
- tsimionescu 5y ago
  Theoretically that wouldn't be a killer issue, since fertile mules are extremely rare, so you could refine the definition to say "is very very likely to produce fertile offspring" (while horses and donkeys breeding is not). The bigger problem are things that have massive morphological differences but can still successfully interbreed, such as dogs, coyotes and wolves. They produce fertile hybrids and there is good evidence that this occasionally happens in the wild, but nevertheless it is rare and they have clear, stable morphological distinctions, even in areas where they overlap. Even worse, that definition is entirely useless for paleontology, as it is impossible to know if two individuals species could even interbreed, nevermind knowing if their offspring would be fertile. Even modern genetic evidence (which is extremely rare for fossils anyway) is very open to interpretation on the matter of potential interbreeding ("Neanderthal" genes in modern humans could more or less as easily be common genes older than both H. Sapiens and Neanderthals - we have far too little evidence to be sure, and no chance of genetic material from an older ancestor).
  - AlotOfReading 5y ago
    If neanderthal or denisovan genes were ancestral, you would be able to find them broadly in African genomes and some of them wouldn't carry adaptations to environments not found in Africa. Instead they reinforce (and inform) our understanding of early human populations out of Africa.

retrac 5y ago

It breaks down with edge cases. There are a few documented "ring species" such as a diverse land-based amphibian around a lake. At all points the adjacent neighbours can mate, but if you take examples from the far side of the lake, they cannot. One species? Two? Infinite? I think it was Richard Dawkins who extended this idea through time. We could mate (sorry) with our immediate ancestors, who could with theirs, etc. and in fact there's a continual chain like that all the way to any other mammal. When did we stop being our ancestral species and become H. Sapiens? No clear line.

lazide 5y ago
It’s the ‘what’s a sandwich’ problem, which is hard. Is a stack of pancakes a sandwich? Is a stuffed pita a sandwich? What is it that makes a PB&J clearly a sandwich, and excludes a stack of pancakes with butter in between - and doesn’t exclude a club sandwich.
- jjk166 5y ago
  If you eat two pancakes with butter between like a sandwich, it is a variant of butter sandwich. If you cut up your PB&J such that you're only eating pieces of bread with some spread on them, that is not a sandwich. The bread must act as a container for the contents during consumption, regardless of ingredients. More generally, the key delimiter for sandwiches is the aspect ratio of the individual items contained by the bread. For something to be a sandwich, all of the major items inside must have one dimension which is substantially smaller than the other two. Sliced meats, bacon strips, cheese slices, sliced vegetables, lettuce leafs, spreads, patties, etc are all valid. Thinly spread peanut butter and jelly between bread is a sandwich, but a bread bowl with a pool of jelly and peanut butter where the depth is comparable to the radius would not be a PB&J sandwich. Flat cheese slice between bread is a sandwich, mozzarella sticks are not sandwiches. Hot dogs are by default not a sandwich, but if you cut the hot dog into thin strips it becomes a sandwich. An oreo is a sandwich but a quadruple stuffed oreo is not. The only commonly accepted sandwich which this definition claims to be a pseudosandwich is the meatball sub.
  - 5y ago

inglor_cz 5y ago

Even if we limited ourselves to the Homo genus, the rule does not work well. Based on the admixtures of Neanderthal and Denisovan DNA in modern humans, we once had a lot of sex with those other humans (and they with us), resulting in fertile offspring, but the differences between us and them are pretty meaningful and probably worthy of not considering us and them just subspecies of the same species. For example, Neanderthals probably could not vocalize in the same way that we do; and being capable of speaking is quite an important distinction. They had very different anatomy, including that of important joints (shoulders).

Scarblac 5y ago

There are far too many edge cases (e.g. ring species), but it's also not practical. How are you going to decide whether two individuals can't reproduce together, or choose not to? What if all you have are some dead specimens? It's mostly based on DNA analysis these days, I think.

Dylan16807 5y ago

I think the fertile offspring test would say a lot of these humanoids aren't different species, though?

FundementalBrit 5y ago
Is the domestic dog the same species as the coyote or wolf? All can interbreed all can have fertile offspring with each other. Then look at the genetic variation between all three species. Yeah this type of science is the stuff which destroys careers...

sdenton4 5y ago

How do you actually test that as a working ecologist, though? Given two geographically and somewhat morphologically district warblers (for example) you would need to convince two of them to breed (after capturing at least one) and then check viability of an offspring. It's not terribly practical... Or, in this case with ancient human remains, there's no way to check viability when all subjects have been dead for a hundred thousand years.