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Plants can have very different pollinators: The wind, insects, and even birds. However, is there a conceivable scenario where a plant could naturally have evolved to depend on humans as pollinators, where the humans (at least in the early stages of development) wouldn't know that they are pollinating the plants?

Note that I'm not after the scenario where a modern developed humanity killed the natural pollinator and thereforehumans now have to provide the pollination themselves; rather I'm after a scenario where a pre-civilized human tribe would though their usual behaviour, without knowing it, pollinate the plant in question, and the plant would actually be adapted to make the humans pollinate it.

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    $\begingroup$ Does it count when a child picks up a dandelion and blows its seeds into the wind? $\endgroup$ – IchabodE Mar 6 '15 at 21:57
  • $\begingroup$ See "The pollinators of Eden" by John Boyd. The flora of the planet used animals until humans arrived, then switched. Since these are humans, the reward is sex - of a sort. $\endgroup$ – RedSonja Mar 7 '15 at 9:47
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Yes, the plant only has to be appealing to humans in some way.

Some of the most successful plants alive today are so bountiful because humans have found them to be beautiful or beneficial in some way (food, medicine, mind altering, etc.). In many cases this is because we've intentionally planted more of them. However, this could easily start out as a process that's not intentional or unknown to the humans.

The humans could then use this plant for its beneficial properties and through that use, spread the pollen. For example, if the plant were visually appealing, humans would pick the plant to wear or display. Transporting the plant to be displayed or wearing this plant while walking through a field of the same plant would act as a pollinator.

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  • $\begingroup$ +1 Good points. Do you know of any plants where the appeal is primarily to humans (or other primates)? Perhaps fruits? $\endgroup$ – Samuel Mar 6 '15 at 19:55
  • $\begingroup$ With biodiversity how it is, it's unlikely to find something that a top level consumer can find benefit from, where something lower down the food chain cannot. There's almost always going to be something below us, animal, insect, bacteria or fungi that would also find benefit in a plant we find appealing. $\endgroup$ – MichaelHouse Mar 6 '15 at 20:03
  • $\begingroup$ @Samuel Coffee, tobaco, maryJuana, etc. etc. etc. $\endgroup$ – hownowbrowncow Mar 6 '15 at 20:44
  • $\begingroup$ @hownowbrowncow Both coffea and tobacco use the substances that humans like, caffeine and nicotine respectively, as defence mechanisms. It doesn't appear that primates were involved (except artificially) with the evolution of those plants. It's not clearly the same case with cannabis, but THC was also likely used for defence rather than for attracting primates. $\endgroup$ – Samuel Mar 6 '15 at 21:00
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I don't see any reason this could not happen. Humans work just as well as pollinators as any other motile creature.

Some things I would consider in this scenario:

  • The idea makes a lot more sense if the humans you are referring to are a nomadic people that make a regular annual trip, meaning they make stops at regular prime locations on a fairly regular basis.

  • The plant would have to have something that humans want/need. Normally this means fruit...unfortunately fruit is the result of pollination. This means you would either need a plant that can fruit and flower simultaneously (which I do not believe happens for any plants) or the plant needs to provide something else in the first place.

There are a host of potential things a plant could provide to get us to pollinate

  • Material for camouflage or decoration
  • Material for making rope or clothing
  • A drug of some sort...could be medicinal or...you know...recreational

I am sure there are more possibilities, hopefully these get some ideas flowing for you.

An additional note...if we are talking prehistoric/nomadic humans it is likely that even adults wouldn't know they are pollinating, I don't know when we figured out how pollination works but I am guessing it was only in the last couple centuries...(I could be wrong on that, complete guess)

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Many people raise Orchids many who raise them cross-breed them intentionally, creating a unique sub-species. These species would not exist without man's guiding hand.

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Are you sure you don't mean propagators, instead of just helping with the pollination?

Pollinators get rewarded, mostly with nectar - which isn't very efficient for humans.

Corn

Corn only exists because humans plant it, its seeds are unable to break free of its husk and self-propagate. "This is not only due to the tight husks, but also because the kernels adhere strongly to the ear and do not easily disarticulate."

However, it can self-pollinate, or cross-pollinate. Farmers don't like it to, because that doesn't lead to the best seed. The best seed for production is created by double hybridization (4 inbred lines). But that veers away from the question.

Many other plants are the same.

Humans are better

Humans also make better pollinators than insects. We're just too expensive to be used as pollinators in most cases. Hmm, that link doesn't have the follow-up to the follow-up, which said eventually the labor costs got too high to employ humans.

But, if you want humans doing it without knowing it, you're going to have issues. Now, some things (pig prohibitions) are done via religious reasons, which are ecologically sound (great Saharan forest elimination) - because some people realized there was a problem, but most humans did not.

Scarification

You might want to move off of pollination, and rely on scarification of the seed (needs to pass through a digestive tract in order to grow) and make it a fruit which is human-specific.

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    $\begingroup$ There seems to be a chicken-or-egg situation with the statement "Corn only exists because humans plant it". The statement is clearly false without any context. Do you mean to say there is a modern, artificially selected, breed of corn that can't reproduce on its own? $\endgroup$ – Samuel Mar 6 '15 at 19:40
  • $\begingroup$ Yeah this isn't correct. There is a reason farmers hire teenagers to de-tassel corn in the summer...Corn seeds are not pollen they are the 'fruit'. Corn travels and spreads like fruit and vegetable seeds, they get eaten...and dropped somewhere else later...with free fertilizer.' $\endgroup$ – James Mar 6 '15 at 20:26
  • $\begingroup$ @samuel No chicken and egg, there was a hybridization and/or species loss of the originators of corn, just like with horses, and cattle. There are no wild cattle, only feral. $\endgroup$ – user3082 Mar 7 '15 at 7:14
  • $\begingroup$ @james Sorry, I meant to write propagation not pollination. And no, corn doesn't spread much in the wild. $\endgroup$ – user3082 Mar 7 '15 at 7:16
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I say stick with the insects. They better organize the way they pollinate and they are a lot faster. If it were a human the plants would die off faster than if it were an insect (preferably bees). This is the main thing people don't think - the way it will affect the economy.

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Some plants have developed seeds which adhere to animals and humans (think of burrs) so they can propagate, but this is the end result after pollination.

What would be needed is a plant which can detach its stamen and adhere to passing creatures in the manner of a burr, allowing it to shed pollen over a wider area. This has some issues, since the pollen is going to become very widely distributed and thus very diffuse. In most creatures (including plants) with sexual reproduction, the "wining" strategy is to deposit more of your reproductive material in the female receptor, hence the very intimate nature of sex. Plants have domesticated bees and other insects to carry large quantities of pollen to the receptive pistils (O.K., coevolutionary pressure caused this development).

If a plant broadcasts pollen, then an almighty amount will be needed (which explains those spring allergies), but a detachable stamen that serves the same purpose would have to be rather large in order to carry enough pollen for this strategy to work "better" than simply broadcasting pollen to the winds like more conventional plants.

So a detachable stamen with barbs or other attachments to hook onto fur, skin or human clothing is needed, and one which can carry sufficient pollen to outcompete plants which simply broadcast their pollen, or have evolved to co-opt insects to do the job.

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