Here is a kind of humour that is all too common in scientific communication; I’ll just show you the caricature, and I think you’ll recognize the shape of it:
Some slogan about how a married man is a slave or a prisoner kneeling and holding a credit card. Some joke where the denouement relies on: the perception that blondes are dumb, male preference for breast size, perceived associations between promiscuity and nationality, or anything involving genital size. Pretty much any one-panel cartoon taken from the Internet.
Should you find any of this in your own talk, here is a message to you: That may be funny to you; that isn’t the problem. To a fair number of the people who are listening, it’s likely to be trite, sad and annoying.
Humour totally has a place in academic speech and writing—probably more than one place. There is the laughter that is there to relieve tension. That is okay sometimes. There are jokes that are obviously put-downs. Those are probably only a good idea in private company, or in public forums where the object of derision is powerful enough that you’re not punching down, but powerless enough to not punch you back. Say, the ever-revered and long dead founder of your field—they may deserve a potshot at their bad manners and despicable views on eugenics.
Then there is that elusive ‘sudden perception of the incongruity between a concept and the real objects which have been thought through it in some relation’ (Schopenhauer, quoted in Stanford Encyclopedia of Philosophy). When humour is used right, a serious lecturer talking about serious issues has all kinds of opportunities to amuse the listener with incongruities between the expectations and what they really are like. So please don’t reveal yourself to be predictably trite.