OFFICIAL33 According to the student, why was it advantageous for early humans to be sensitive to bitter tastes?

[00:00.00]NARRATOR: Listen to a conversation between a student and his biology professor.[00:07.57]MALE STUDENT: Professor Landry?[00:09.90]FEMALE PROFESSOR: Hi, Dennis. You are right on time. [00:11.75]Come on in and have a seat.[00:13.04]MALE STUDENT: Great! Thanks.[00:16.57]FEMALE PROFESSOR: So like I told you in class, I just wanted to take a few minutes to meet with everyone to make sure your class presentations for next week are all in order and coming along well. [00:26.97]And as you know, you are supposed to report on some area of recent research in genetics, something, you know...original.[00:33.54]MALE STUDENT: Well, I think I found just the thing! [00:36.13]It actually occurred to me a couple nights ago while I was eating dinner in the cafeteria...[00:40.40]Tell me, Professor...do you like broccoli?[00:42.95]FEMALE PROFESSOR: Broccoli? You mean, the vegetable broccoli?[00:46.65]MALE STUDENT: Yeah.[00:47.39]FEMALE PROFESSOR: Well... I guess not really...[00:51.40]MALE STUDENT: Me neither. I have never liked it—or most other vegetables ,for that matter: brussels sprouts, asparagus, cauliflower—you name it. [00:58.86]They just taste bitter and...well,nasty to me.[01:02.16] My mother always called me a picky eater.[01:04.30]FEMALE PROFESSOR: O-kayyy...and?[01:06.64]MALE STUDENT: And so I got to wondering: I mean, I am obviously not the only person like this. [01:11.81]So is this just because of some, like trauma from our childhoods? [01:16.12]Some bad experience we've had with vegetables? [01:18.61]Or could there be some genetic explanation for why some people are picky eaters and others aren't?[01:23.98]FEMALE PROFESSOR: OK. I see. Well, I suppose it's a possibility.[01:28.13]MALE STUDENT: Actually, it turns out it's more than a possibility.[01:30.98] I started doing some research in the library that night and I found out that a biologist at the National Institutes of Health has been looking at that very question recently.[01:40.20]FEMALE PROFESSOR: Well, I guess that's not too surprising. [01:42.57]And this is great stuff actually. [01:45.27]So what's the verdict?[01:46.85]MALE STUDENT: Well, this guy seems to have discovered a particular gene that actually makes it possible for people to taste the bitterness in certain green vegetables. [01:54.92]But people who have a mutation in that gene cannot taste the bitterness.[01:59.15]FEMALE PROFESSOR: Well, that's certainly fascinating! [02:02.69]But...so this biologist is basically claiming that people who like to eat these vegetables actually have some sort of sensory deficit? [02:10.97]Sort of makes us picky eaters than normal ones, doesn't it? [02:14.66]I mean, that's kind of turning things on their head, isn't it?[02:17.48]MALE STUDENT: Well, then again, it wouldn't be the first time, would it? [02:20.69]Think of it this way: humans originally needed to have a stronger sensitivity to bitter-tasting foods so they could learn what plants were good for them and which ones might be poisonous. [02:30.59]But at some point, as people figured out what they could safely eat, this need became less crucial and a segment of the population lost that ability.[02:39.09]FEMALE PROFESSOR: OK. Well, you make a compelling case. [02:42.82]I can't wait to hear more about this when you deliver your report.