Hibernation: Not Just For Picnic Basket-Stealing Bears Anymore

I suggest that since humans are mammals we are susceptible to hibernation characteristics. As always, I will offer supporting evidence of my claim. I am good about giving evidence, my weakness is in the weakness of my evidence, it's usually nothing but anecdotal - but then what evidence isn't anecdotal (think about it). Example one: years ago I was working at Subway. My friends would come in all the time in the afternoon. During the summer we'd go over to someones house and play rock and roll music. Most of us played guitar or something. They could come in at 4pm and want to go do something when I got out of work at 5pm and I'd go. Then it turned to Winter and it was dark and cold by 5pm. My friends would come and ask if I wanted to do something and I'd say it was late and I wanted to go home. Nothing in the situation changed except the temperature and amount of light from the sun still visible (how's that for an accurate statement?). I figure it must be the cold and dark that make me want to just go home and not be out. I guess that's really the only example I have to give, it just happens a lot. I'm noticing it again now as Summer is ending. It is still light until 7pm or so, and it's not so cold that I need a heavy coat yet, but I'm starting to feel like not going out in the evening. Either I'm feeling some hibernation tendencies or I'm developing evening-specific agoraphobia. I've lost interest in this topic rather rapidly. I would at this point do some research on hibernation and make some ridiculous comparison to human brain function or behavior, so ridiculous that you would believe it, but I think I'd rather not. Another time, perhaps.