Financial advisors tell me that mergers and acquisitions have been their biggest activity during the past year. It doesn’t look to change. The year ahead, they say, feels much the same. Continued mergers and acquisitions in 2016, two entities coming together in order to survive.

I see evidence of it in today’s Wall Street Journal. Articles highlight Dow and DuPont’s next steps together, Halliburton expanding, and more. I can hear the chanting in financial businesses throughout the land: “M and A is here to stay!”

Have you been involved in a merger and acquisition? Has your leadership been tested in the unique experience of bringing two separate sets of followers together? I wonder what you would say about it.

Naturally, as a consulting leadership historian, I think in terms of time. The time before now. Whenever two things combine into one in the present moment their two pasts collide as well. And just as importantly, you have two histories also colliding—the history being the story of the past that gets recalled, remembered, and re-told. Like the confluence of rivers, the joining of two sets of time will be seen on the surface and in the depths.

The signing of the agreement to merge and acquire is brief. The effects of two pasts and histories interacting, however, will last a very long time.

Be prepared for new waters.