1/ Here are my notes from @robertwrighter's book - Nonzero: the logic of human destiny. I enjoyed the book very much.

The basic premise of the book is that history has a direction which favors co-operation and non-zero sum games, and that causes an increase in complexity.

2/ Starting from the first replicating molecule which co-operated with an outer layer to form first proto-cell, evolutionary and cultural history is full of examples where two entities come together to survive and progress a lot more than they would have done individually.

3/ This co-operative entity fares much better than two individual entities because of specialization. If two entities are in the same boat - that they win together or lose together - then trust is implicit.

4/ In a non-zero sum game, trust causes entities to focus on what they do best.

For example, eukaryotic cells - the ones animals and plants have - emerged when two proto-cells merged, and one took the role of energy generator (mitochondria), the other specialized in protection.

5/ Some scientists believe that even nucleus in a cell is a result of an early cell merging with another cell.

So M&A is not a recent phenomena, entities have been merging because of common interests ever since life started.