This one probably falls into the realm of science fantasy — but then, people have said that before about a number of things and turned out to be wrong.
There have always been fanciful ideas about how to solve the perennial human problem of famine and plain old food insecurity. They started, I assume, with the first person to say “hey, let’s stay in one place instead of wandering and we can plant these seeds in the ground near our place so we always know where to find food.”
Unless the first person to say that was persecuted as a blasphemer against the nomad gods. Then, maybe it was the second person to say it, or the tenth. Which is a scenario that has occurred to me before — it’s the premise of my short story, The Always-House People. (which happens to be free, by the way)
But back to the subject at hand.
There was Swift’s A Modest Proposal with its satirical suggestion of roast children dinner; more seriously, churches and monarchs and charitable organizations and nation-state governments have taken hands at feeding the famine-stricken throughout recorded history. Even more time and energy has been devoted to increasing crop yields through all sorts of means — different growing methods, developing better fertilizers, breeding plants and livestock for improved yields, and lately (and controversially in many cases) directly manipulating the DNA of plants and livestock. And so on.
Closer to this somewhat fanciful idea of green humans sunbathing for part of their sustenance is the proposal to shrink the future human race to an average height of 50 centimeters (about 20 inches). Less biomass, less food and fewer resources to maintain, and therefore less famine — plus less pollution, less scarcity of other resources, and so on.
It would be easy enough to do both, I suppose. Imagine being a tiny green human sunbathing for breakfast and then lunching on a slice cut from a rabbit ham so large in comparison to you it’ll last your family a week.
Any suggestion to fiddle with the genes of just about anything, though, wakes the memory of thousands upon thousands of science fiction tales of technology gone wild. Or, mostly ancestral to those, tales of magic and wishes gone wrong — think of the old tales of the Golem and Pandora’s Box and the Garden of Eden and the Tower of Babel. All stories in which the quest for knowledge is somehow destructive.
Those tales are pretty irresistible as a reader or a writer. Things do go wrong. Actions have unintended consequences constantly. Human history and storytelling revolve around such stories because they’re stories of life and trying. Tryers fail.
So I hope this story gave you a little chuckle, and maybe inspired a thoughtful moment. As for how possible it is… I’m not a biologist of any description. But it would amuse me to no end if we turned out to be the LGMs, the little green ‘men’ aliens, accidentally pollinating one another.