In fact, are we who we are or are we a host of aliens? On our body, in fact, there's a whole bunch of aliens including the fleas, the mites and all the worms and all these things. Don't tell me that you don't have. You do have. It's just so far it has not surfaced yet. So let me give you one example. Who are we? So these are not human beings but then I think if you use that as a case, that illustrates the point. I picked up this article from a science journal and it's talking about a hyena. So it turns out that they find that in Africa, the hyena, they do have tribes. One tribes, those living on the Hong Kong Island, they hate those one in the living Kowloon. They don't talk to each other. They don't identify, mate with each other. And so basically, whenever they see each other, they would simplify fight and try to stay away from each other. So what happened? So people identify them and collect their DNA to look at what the DNA is like. It turns out their DNA were more or less exactly the same. Like the same species, no difference. In fact they can, as a species, they can cross fertilize each other and produce the next generation. So their offspring is the same species. How did they establish a tribe? The funny thing is that, then they look into actually what kind of bacteria is associated with them. And they find that one tribe and the other tribe, on their body, they have a different community of bacteria. So what did they do? Hey, they secrete all the whatever secretion on the body, sweat and all these, and then depending on actually what bacteria they have, the bacteria would go through the fermentation and create metabolites which smell differently. And now these two tribes, they simply hate that smell. And for some of them, they simply get used to a certain smell. I like that smell, and whenever I smell something different, go away. So thus they become enemies of each other. So in a way, even those individual which is on the body, all this living E. coli or bacteria, they all make them different even though genetically they are identical. Now so what I mean is that, that identity issue simply goes away. And what happens is that there are some other interesting organisms. So this is the organism which I'm very interested in, which is called convolutriloba. It is kind of like a flat worm. You don't see them very often but if you go to aquarium, sometimes you'll see this greenish, sometimes a pale grey slug crawling around. But very tiny, about one millimeter in size. So what happens is that this particular species is funny. When they are born as an egg, they won't be able to survive very well. But very soon when they grow a little bit bigger, somehow they will have the ability to acquire some of the algae around and they incorporate them into their body. So that the algae becomes part of them as a parasite, you can call that. But that actually is some mutualistic interaction, they become symbiont so they work together. And the algae would absorb the sunlight, take the energy that put things into order. Now transfer the energy to this individual so they can be crawling around and without eating because energy will be provided for them. It's like a battery embedded in them. So think about that. If you have this algae incorporated in your body, you don't need to go to lunch. You don't have a chance to go to lunch today, but what you can do is simply you can walk around in the lawn for a while and then go back and you energize. So that is what it is. And in fact, these kind of things is happening multiple times. This is another snail, multi-cellular organisms. They also do the same thing. They incorporate algae into their body, so that they can use the algae to generate energy so they can go around. Now so what it means is that, these individual, they must survive in a certain way. Their identity is not defined just by their DNA but defined by what they incorporate, what they are living together with and all this.
