It's intriguing. I'm somewhat unsure about the "because" in the study: "…because the two organisms need each other alive." (Perhaps the National Geographic was the culprit here; it may have glossed over the pure research.) Cause and effect are slippery. Usually "and so" is safer than "so". I do this thing, and so you are able to do whatever¹ as opposed to I do this thing so you are able to do whatever² Interesting. Thank you. ¹coordinating conjunction and merely allows hand-holding between (independent) equals ²so, without the conjunction, ascribes cause and effect; this was the reason I did my part —For English students or anyone who has difficulty with this, including readers on this forum: If you don't understand it, always just stick with "and so", and you won't go wrong. :-)
