What benefit do small spaces provide in the formation of organic molecule? ?

The benefit that small spaces provide in the formation of organic molecules is that it creates an additional surface area on which reactions can take place. A larger surface area allows biochemical reactions to take place more frequently, thus increasing the rate of the biochemical reaction. 

explanation:

the fossil record extends back to a dog-like ancestor some 55 million years ago, which gave rise to the first horse-like species 55 to 42 million years ago in the genus eohippus.