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Evolutionary Anachronism

The avocado may be an example of an 'evolutionary anachronism', a fruit adapted for ecological relationship with now-extinct large mammals (such as giant ground sloths or gomphotheres). Most large fleshy fruits serve the function of seed dispersal, accomplished by their consumption by large animals. There are some reasons to think that the fruit, with its mildly toxic pit, may have co-evolved with Pleistocene megafauna to be swallowed whole and excreted in their dung, ready to sprout. No existant native animal is large enough to effectively disperse avocado seeds in this fashion. If so, the avocado occupies an ecological niche similar to that of the mango of Asia.

Basically, this tree evolved because there was an animal large enough to poop out the seeds in dung from which it could sprout? Something to think about when you're cutting them open and trying to grow them.

It's also interesting that they're not toxic to us.

The form of the avocado fruit today may be more of a result of a past ecological relationship with magafauna than the current relationship with humans, monkeys, and other extant animals. Barlow (2002) posits that the avocado is "haunted" by the "ghosts" of the glyptodonts, toxodons, gompotheres, and groundslots. The Persea species that live along the Gulf Coast have fruit that are about the size of blueberries, small in comparison to the avocado. Avocado pits are soft and unprotected, unlike other fruit tree seeds such as canistel (Pouteria campechiara), which has a mild-flavored seed with a tough coating. Instead, the avocado relies on bitter toxins to deter damaging the seed through digestion. The avocado pulp also contains laxaitives, which quicken the seed's trip through the animal's digestive system, reducing the chances of damage by the digestive juices. Only megafauna would have been large enough to swallow the fruit and the pit whole, which would have helped the avocado disperse its seeds. The seeds pass through in a "fertilizer" of feces. Today, elephants in Africa disperse fruit tree seeds through their feces, including the non-native avocado and American papaya (Carica papaya) (Barlow 2002).
http://blm.academia.edu/AmandaJLandon/Papers/406186/Domestication_and_Significance_of_Persea_americana_the_Avocado_in_Mesoamerica

So the biggest reason seems to be that the skin has laxatives which implies the whole fruit was eaten, skin and all. There is no existing native animal large enough to do this.

Ground sloths are a diverse group of extinct sloths, in the mammalian superorder Xenarthra. Their most recent survivors lived in the Antilles, where it has been proposed they may have survived until 1550 CE; however, the youngest AMS radiocarbon date reported is 4190 BP, calibrated to c. 4700 BP for Megalocnus of Cuba. They had been extinct on the mainland of North and South America for 10,000 years or more.

They think they evolved while South America was isolated. It was thought to be uninhabited by humans when people were crossing the Bering Land Bridge 15,000 years ago and they migrated south through the Isthmus of Panama.

So maybe in that 5,000 years or so, they were hunted to extinction and those hunters had the ability to eat the avocados? They probably also tracked these animals through their poop, etc.

So, the avocado represents how much of a threat we are.

http://upload.wikimedia.org/wikipedia/en/7/73/Giantslothtex1.JPG

This has also apparently affected the Devil's Claw which is another evolutionary anachronism related to extinct mammalian mega-fauna seed dispersal.
http://en.wikipedia.org/wiki/Acacia_greggii
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38 comments
 
Interesting to see this post come through my stream just as I finished pealing and mashing avocados. I did discover that avocados are poisonous for chickens. We have chickens and I don't remember exactly how I learned this, but my children area always fascinated by this random fact. They always remind me not to give avocados to the chickens.
 
Or grapes/raisins to dogs. Weird, eh?
 
+Maria Stepanov Sommerfield I had one earlier today in a salad. My girlfriend had one just now & told me about it.

Apparently you have to cross-pollinate them before they show fruit too. Anyway, at least we still have them around to enjoy.
 
They will grow from pits taken from avocados you buy in the store, we've done it several times. In fact, it's best not to put them into the compost, because they'll sprout before they decompose.

Much harder to grow them to maturity, though.
 
What ecological niche, exactly?

Also, I didn't know that, +Craig Froehle. My uncle had dogs that loved to eat grapes (and melons).
 
Any model is just an approximation, so it will certainly meet exceptions. Theory of evolution is just a model, right? :)
 
+Gopindra Hannigan Oh, yeah, many dogs like to eat grapes, but there's something in grape skins (IIRC) that is toxic to dogs.
 
+Gopindra Hannigan The form of the avocado fruit today may be more of a result of a past ecological relationship with magafauna than the current relationship with humans, monkeys, and other extant animals. Barlow (2002) posits that the avocado is "haunted" by the "ghosts" of the glyptodonts, toxodons, gompotheres, and groundslots. The Persea species that live along the Gulf Coast have fruit that are about the size of blueberries, small in comparison to the avocado. Avocado pits are soft and unprotected, unlike other fruit tree seeds such as canistel (Pouteria campechiara), which has a mild-flavored seed with a tough coating. Instead, the avocado relies on bitter toxins to deter damaging the seed through digestion. The avocado pulp also contains laxaitives, which quicken the seed's trip through the animal's digestive system, reducing the chances of damage by the digestive juices. Only megafauna would have been large enough to swallow the fruit and the pit whole, which would have helped the avocado disperse its seeds. The seeds pass through in a "fertilizer" of feces. Today, elephants in Africa disperse fruit tree seeds through their feces, including the non-native avocado and American papaya (Carica papaya) (Barlow 2002).
http://blm.academia.edu/AmandaJLandon/Papers/406186/Domestication_and_Significance_of_Persea_americana_the_Avocado_in_Mesoamerica

So the biggest reason seems to be that the skin has laxatives which implies the whole fruit was eaten, skin and all. There is no existing native animal large enough to do this.
 
Ground sloths are a diverse group of extinct sloths, in the mammalian superorder Xenarthra. Their most recent survivors lived in the Antilles, where it has been proposed they may have survived until 1550 CE; however, the youngest AMS radiocarbon date reported is 4190 BP, calibrated to c. 4700 BP for Megalocnus of Cuba. They had been extinct on the mainland of North and South America for 10,000 years or more.

They think they evolved while South America was isolated. It was thought to be uninhabited by humans when people were crossing the Bering Land Bridge 15,000 years ago and they migrated south through the Isthmus of Panama.

So maybe in that 5,000 years or so, they were hunted to extinction and those hunters probably developed the ability to eat the avocados? They probably also tracked these animals through their poop, etc.

So, the avocado represents how much of a threat we are.

http://upload.wikimedia.org/wikipedia/en/7/73/Giantslothtex1.JPG
 
Neat! So, what animals were responsible for the mango's present form?

+Craig Froehle, I didn't know that. Snopes says macadamia nuts and onions are also toxic to dogs (along with the well known cocoa toxicity).
 
That bit about the avocado being haunted by the ghosts of dead megafauna was a bit over the top, though!
 
I think that's just a neat way of saying that evolution works on many levels. Like a meta-evolution. This is not directly related but it reminds me of a recent conversion about the implication of reviving extinct animals and plants and what that might mean for evolution.
 
Apparently the author is a unitarian universalist and an evolutionary evangelist trying to marry evolution to her religious belief in a more distant creation which I'm assuming is the big bang.
 
But they are surviving now being a large mammal thinks their tasty and doesn't takes care of all the seed dispersal for it, what better strategy is there than that?
 
Yea it's been domesticated. So it's evolving in a way that depends on our intelligence? Genetic engineering would be an extension of that.
 
Just imagine how slow those huge sloths must have been, must have been an easy kill?
 
+Jonathan Langdale The problem was that the predators of the time were a lot smaller than the giant ground sloths, so the sloths didn't really fear much. Which, I guess, is why they were permitted to evolve into...well...sloths.
 
What an interesting and unique piece! More reasons to love G+.
 
Not really sure we need comments such as "waoooooooooooo",but besides that a nice unexpected diversion, thanks. Also had avo tonight in the form of a guacamole - different every time I make it and never a flop :) Also, wondered why the prevalence of those calling pips pits. They are pips people, "pits" are holes in the ground. Ppptht! ;)
Also great for kids to grow suspended in a jar of water by three toothpicks - although legend has it, these will never produce fruit (presumably because most commercial cultivars are grafted?) It occurs to me that the large size of the piP allows a good survival rate of any germinating pips. Oh, and if you can answer all those sub threads, good luck to you. No-one else in my history of posting has EVER done so. Take that.
 
the picture makes me wanna drink avocado juice
 
What a bunch of malarcky posted above. This beautiful fruit was created by the Almighty Creator God; it is a nutritious food for humans and others in the animal kingdom and has not changed its form from when it was first created.
 
Avocado factoid: Full sized, fruiting, avocado trees grow here in Chico California at 39.7º North. Possibly the northernmost avocado trees in the world grown outside a greenhouse. A few people even sell the local avocado variety at the farmer's market.
 
Oh, and thanks for this thread reminding me how much I enjoy the word megafauna.
 
nice shot, beautiful and delicious avocado
 
+Jonathan Langdale It still works. Humans make the effort to peel the fruit, eat the flesh, then wonder what to do with the seed.
So they either put it in a pot filled with earth, or they throw it on the compost x).
+Sheree Renard If facts concur with your belief, you ignore the facts? Must be a tough world to live in.
 
+David Röll Which makes you wonder if the avocado has evolved at all in respond to human seed dispersal vs the now extinct mammalian megafauna method.

Are humans favoring more or less ripe fruit due to distribution methods?  Or, maybe faster or slower ripening strains so that you don't have to wait too long to make your guacamole?
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