Why We are Alone in the Galaxy: Marc Defant (Full Transcript)

Marc Defant is a tenured professor of geochemistry at the University of South Florida and studies volcanoes and the origin of the continental crust.

Here is the full text of Marc’s talk titled “Why We are Alone in the Galaxy” at TEDxUSF.

 

Marc Defant – TEDx Talk Transcript

I wrote a book about the history of life, and I started noticing when I did my research that there were the statistically improbable events seemingly that had to occur in order for us to get intelligent life here on our planet.

And SETI has been now searching for the extraterrestrial intelligence, they’ve been searching for life for 54 years and they, of course, haven’t found any intelligent life.

And so I got to thinking maybe they weren’t finding it because it’s extremely difficult to occur, evolutionary or whatever.

So tonight what I’d like to do is, I’d like to give you 3 examples of these statistically improbable events but please keep in mind that there are literally hundreds of these events which need to occur in order to get intelligent life on this planet, in my opinion.

Well, I need to go back to the Big Bang and talk a little bit about the Big Bang Theory, and I hope to god that when I said the Big Bang Theory, the first thing that came to your mind wasn’t the television show, because we’re all in trouble if that’s the case, and it could be a long talk, too.

Well, in the Big Bang, 13.8 billion years ago, there was hydrogen and helium, that’s it. So scientists recognize that we need another source for all the other elements that we find in our universe and we now know that source is a supernova.

And a supernova is literally the death of a giant star. It collapses in on itself, it forms all of the elements in the periodic table, other than hydrogen and helium, and then, it explodes and it sends that material out and into its local space.

Well, now I want you to picture something called a solar nebula. This is a gaseous cloud that once existed out there that later collapses to form our solar system. And that cloud was originally enriched only in hydrogen and helium.

So we have to have all of these supernovae erupting out there and enriching that solar nebula in all of the elements requisite for intelligent life in particular on our planet. And if we don’t have that, then we can’t get an intelligent life. And then at some point, there has to be a supernova nearby our solar nebula which forces it to collapse.

Now how do I know that there was a supernova out there that forced our solar nebula to collapse?

Well, I think that’s one of the most interesting scientific discoveries of all time and it doesn’t get much press, so I’d like to share it with you tonight.

The Allende Meteorite is believed to be material that formed from our solar nebula as it was collapsing to form our solar system. One of the reasons we know that is it has calcium-aluminum inclusion in it that dated to 4.56730 billion years ago. So, that’s the oldest date that we find in our solar system, and we now use that date as the beginning or the origin of our solar system.

Well, in this calcium-aluminum inclusion is a strange thing. We find an isotope of magnesium, called magnesium 26, and we shouldn’t have magnesium in calcium-aluminum inclusion. So scientists were puzzled over this, and they recognized though at some point that magnesium 26 is the decay product of aluminum 26.

Aluminum 26 has a relativity short half-life of 717,000 years, so that means that in 7 to 10 million years, all of the aluminum 26 is going to decay away to magnesium 26, we don’t have any aluminum 26 on the planet today that’s because it all decayed away billions of years ago, when it first formed from a supernova.

So, I think you can see here what’s happening. We had a supernova nearby our solar nebula, and injected it with all of the requisite elements including aluminum 26 and forced it to collapse, and as it collapsed, the calcium aluminum inclusion is formed, rich in aluminum 26, and that aluminum 26 is then, decayed to magnesium 26, hence the reason we have magnesium in this calcium-aluminum inclusion.

So, I don’t know, I think that is an incredible scientific discovery. I’m a little prejudiced, but think about that, we can take things that we see today, we can look at them, we can study them, and then, we can extrapolate back to things that were happening 4.5 billion years ago. It’s amazing, I think.

And where does the statistical improbability come into play here?

Well, think about what has to happen. You have to have our solar nebula out there with just hydrogen and helium in it, to begin with. And then, you have to have all the supernovae going off which inject it with all of these elements bigger than hydrogen and helium, and just the right amount, and none of them can force our solar nebula to collapse.

And then, we have to have this supernova, which we know occurred close enough to our solar nebula to force it to collapse. And when it collapses, at just the right time, when our solar nebula has just the right composition. Then, it collapses and it forms and eventually, it leads to us.

Well, that seems remarkable to me. An improbable event if there ever was one, and we’re here possibly as the result of it. Well, that’s the first statistically improbable event I’d like to talk about tonight, but the second one has to do with this graph.

This is a graph of a log of brain mass versus the log of body mass, and one of the things I’d like to show on this diagram is that I’d like to show the relative intelligence of animals on the planet, and in order to do that you can’t just show brain mass, you have to show log mass, or log of the body mass, and I think you can see what I’m talking about when you see of this field.

This is the field for fish, amphibians and reptiles and as you can see for a given body mass, throughout these creatures have a lower brain mass compared to many of the other elements, or I should say animals on our planet.

Well, you’re not going to find any brain surgeons in and among the fish, amphibians and reptiles – that’s for sure.

But where do the mammals fall? The mammals fall at much higher brain mass for a given body mass and that’s because mammals have a neocortex, and that’s what evolved into our grey matter. So it’s not surprising to see that the mammals fall higher than the fish, amphibians and reptiles.

And then the primates, you can see where they fall, they’ve some of the largest brains in the animals’ kingdom and I’m going to talk a little bit more about the primates and explain why they might have gotten those big brains.

But first I want to talk about and concentrate on this red dot. There is a red dot falls to a low body mass and very high brain mass, and that’s where people that come to TED Talks for, but you might like to know. OK.

What we all learn from Jurassic Park that the dinosaurs were geniuses, I mean, think about this, they learn how to open doors, for God’s sake. But I’m here to tell you that they weren’t as smart as we think they were in Jurassic Park was lying to us.

Look where the dinosaurs fall, towards very high body mass but relatively low brain mass. They weren’t the sharpest knives in the door; that’s for sure. Well, now once we get the dinosaurs and we see how they fall, this brings me to an important point, and that is about evolution, and that is evolution doesn’t always select for the brightest creatures.

In the case of the dinosaurs, they were selected for their large body mass, and they were immensely successful. They ruled the planet for 135 million years.

And what were mammals doing during that time?

Well, the mammals first appeared in the Triassic about 200 million years ago. They were little tiny creatures scurrying around trying not to get stepped down by the dinosaurs. And they were that way throughout the entire Mesozoic, and if it weren’t for the demise of the dinosaurs, I’m going to suggest to you that we’ll still be little tiny creatures running around and I wouldn’t be up here talking to you tonight.

And it’s that demise of the dinosaurs that leads me to my second improbable event and that has to do with the destruction of the dinosaurs. These are the Alvarez’s. They’re standing next to what we call the Cretaceous Tertiary boundary. It’s an ash layer, and that ash layer was deposited by – the Alvarez’s discovered this – 66 million years ago by a meteorite impact destruct. It hit Mexico — well, it didn’t hit Mexico.

66 million years ago, Mexico wasn’t there – but get my point – but it hit in that area, and it sent ash to the atmosphere, and that ash was carried around the planet by the atmospheric currents. It caused the planet to be darkened for months, and it stressed the largest animals on the planet, the dinosaurs, that wiped out every one of them and here’s something a lot of people don’t know, it killed off 75% of the species on planet Earth, it was a horrendous event.

Now, where does this statistical improbability come into play here?

Well, think about this. The Alvarez’s discovered that the meteorite was 10 km in diameter, if that meteorite was a little bit bigger than 10 km, it might kill off all life on the planet. And if it’s a little smaller than 10 km, it might not kill off the dinosaur, and we’d still be little tiny creatures.

So I hope you can see the fine-tuning that required here, and the fortuitous event this must have been. Think about it, we have to have just the right size of the meteorite, striking planet Earth in order for us to get here, that seems like a statistically improbable event to me, and I hope it does to you, too.

So what happens after the dinosaurs are gone?

Well, we see the mammals radiated out into all of the niches previously held by the dinosaur. One of the areas that they radiated into are the trees. And the trees are where we get primates. And when you’re jumping around from limb to limb, a lot of the things that are required of that process. There are things that need big brain power, a lot of computing power, so we see the big brain.

Let me give you a couple of examples. The primates have three-dimensional vision. They have color vision, and they have these digits, and it takes a lot of fine motions to move these digits. So it takes immense computing power, and not surprisingly, these things that were selected for in the primates.

Well, they also come within the big brain. And so we see big brains in primates as you saw in that graph I’ve shown earlier.

Now, I’ve heard from a certain sectors that we were given digits, so that we can type on computers and throw footballs, but that’s not the case. We have digits in three-dimensional vision in color because we evolved from creatures that once lived in trees. I hope that’s obvious.

Well, here’s where I’m going with this, and that’s we need all of these events to take place, and primates we need to get then out of the trees and onto the ground. And this is where the third statistically improbable event takes place that I want to talk about tonight and has to do with the East African Rift zone.

The East African Rift zone started tearing Africa apart about 10 million years ago. And it has been rifting Africa apart ever since then. The faults in red here, the large triangle, there are big volcanoes – and they are in red. And those blue dots, those are Hominin localities, but most of the main ones are on there.

And these hominin localities are where we find fossils of upright walking bipedal creatures. If somebody says to you we are all of these missing links, show them this diagram, that where all the missing links are, they’re everywhere out there.

We not only have our direct ancestors, we have our first and second cousins, you name it, they’re out there. You know, that 7 million years ago we found a fossil that was walking in East Africa upright, and it had bipedal motion, it had a brain about the size of a chimpanzee, and it’s just when genetic clocks tells us it should be there. So I think that’s amazing.

So what has to happen to cause this bipedal walking motion and the big brains that we have today?

Well, it has to do with the East African Rift zone. The East African Rift zone cause conditions to dry and become arid in East Africa. It destroys the jungle and it forces the primates out of the trees and onto the ground.

And then we see these amazing things happened, we start to see these creatures that are walking upright, we start to see them develop amazing size brains, and it’s like nothing in the history of life on the planet, I’m not kidding you. We don’t see this anywhere in the history of life.

I’m going to give you an example here. Australopithecus, about 3 to 4 million years ago, it was an upright walking creature, that had a brain, just a little bit bigger than a chimpanzee’s, and this Australopithecus evolves into stone tool makers, then Homo Habilis, Homo Erectus, and then us Homo Sapiens and it moves on Africa a hundred thousand years ago populates the planet, us.

And that happens because of aridity in East Africa. It’s an amazing event, in my opinion. And where’s the statistical improbability come from? Well, think about this, if this was an East South American Rift zone or an East North American Rift zone, we might not be here. That rift zone need to cause aridity where the primates are, and not just the primates, the largest primates, the great apes. So it has to occur in East Africa.

Well, that’s a fortuitous event, an improbable event. Now, I don’t want to come from an anthropocentric point of view tonight. I’m not suggesting that the god made all of these statistically improbable events occur, so that we would be here. That seems mildly arrogant to me.

No, what I’m suggesting is that in the nearly infinite universe that there might be few localities where you have all of these statistically improbable events occurring at just the right time to get an intelligent life like us. But in most of the places out there, and I’m talking about the rest of our galaxy and most of the universes, it might have a few of these statistically improbable events, but not all of them, and not in the right order. And that’s why I think that SETI is having trouble finding intelligent life.

Now I’m not on some campaign to shut down SETI, I’m not on the warpath to get rid of SETI, that’s not my point here. That’s a relatively negative point of view, and that’s not the way I want to finish.

I want to finish with the positive point, and I hope you recognize my point here is that life is very very rare. I mean think about how difficult it was to get our species here, and then, I want to point out to you that every one of you is very rare.

Think about this. Every one of your ancestors, and I’m talking about your parents, your great-grandparents, your grandparents, all the way back to the first cell. Every one of them had to be successful at least one thing, and that was getting their genes passed on to the next generation.

And if they weren’t you wouldn’t be here. I think of the gazillions of things that had to happen in order for you to be here. Well, it’s an astounding thing.

So what I would like to leave you with tonight is that life is rare, life is precious, and we need to take advantage of. And I can’t see it, I don’t think of any better than John Lennon.

So I’m going to leave you with John Lennon’s words tonight, and I want to thank you very much for this opportunity to come and speak to you.

Thank you.

 


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