Evolving rats are ticklish

Here is more evolution news:

Even laboratory rats have been shown to chirp delightedly above the range of human hearing when wrestling with each other or being tickled by a keeper -- the same vocalizations they make before receiving morphine or having sex. ...

``Tickles are the key,'' he said. ``They open up a previously hidden world.''

Panksepp had studied play vocalizations in animals for years before it occurred to him that they might be an ancestral form of laughter.

``Then I went to the lab and tickled some rats. Tickled them gently around the nape of their necks. Wow!''

The tickling made the rats chirp happily -- ``as long as the animal's friendly toward you,'' he said. ``If not, you won't get a single chirp, just like a child that might be suspicious of an adult.''

Rats that were repeatedly tickled became socially bonded to the researchers and would seek out tickles. The researchers also found that rats would rather spend time with animals that chirp a lot than with those that don't.

Yeah, I tried that with my wife. Maybe the rats are evolving to be more like women.