The mesolithic bridged the time between paleolithic hunter-gatherer societies and more sedentary neolithic communities that practiced agriculture and animal husbandry. It came after the last ice age, which in Europe gave way to landscapes of forests and swamps, IIRC. People continued to make stone tools and archeologists have recovered some human figurines from this period.

This is basically all I know. Do we know anything else? Is there any particularly educated speculation?