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(dramatic music)

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Great white sharks are

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exquisitely designed predators.

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18-foot-long adults tip the scales at over one ton.

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They chase their prey at 35 miles per hour,

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and then secure it with 300 lethal, replaceable teeth.

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These are the Ferraris of the shark world,

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and like most fine-tuned cars, they're extremely complex.

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Despite being the most famous sharks in the world,

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scientists still know little about them.

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Great white sharks are huge animals,

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and yet they are able to move in

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some of the most inhospitable and remote habitats on Earth,

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and as a result, we humans just don't see them very often.

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Evolutionary biologist Dr. Toby Daly-Engel

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has uncovered some of the secrets

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closely held by these elusive animals.

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By using a genetic process made popular for crime scenes,

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she's created a great white family tree.

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The DNA analysis reveals that the great whites

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may be great mothers, possibly great siblings,

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and maybe even great partners.

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Genetics is a really useful tool to help us

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look at great white shark behavior

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and habitat use in a different way.

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Traditionally, in order to study great whites,

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you have to catch them and attach a tag,

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and then you have to be able to follow them.

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With genetics, we don't actually have to necessarily

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tag a shark, we can just get a tiny sample

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as it's passing by and we can get enough information

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about that animal to compare it to other great white sharks

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all over the world.

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Toby is fascinated by sharks,

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but only recently spent time with great whites.

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When I got a chance to see a great white shark

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in the water for the first time,

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the top of my head kind of blew off,

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and it was just amazing.

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It was like seeing a celebrity.

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That's why she's traveled

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to a remote Mexican coast off Baja, California,

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hoping to learn more about great white shark

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mating and reproduction.

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The area where we went to see if we could find

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great white shark pups was pretty remote.

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It was a really amazing place,

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really incredible arid desert ecosystems

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right up against this flat, flat coastal bay

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that had just chock full of gray whales

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and as it turned out, baby great white sharks.

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Research seemed to point to the shallow bay

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as the place to find infant shark pups,

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possibly born to females from Guadalupe Island,

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roughly 220 miles away.

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They will stay in the nursery habitat

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until they get big enough to where they can rejoin

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the adult sharks in the better offshore foraging areas.

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Juvenile white sharks have been spotted

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in other parts of the world, but not many.

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Toby's team worked with the local fisherman

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to find infant great whites in the bay.

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They used a tested method to catch

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and safely release the baby sharks.

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(tense music)

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Within a few days, they caught and safely released

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12 infant and juvenile great whites,

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but not before Toby took individual samples of their DNA.

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I was going for a very, very small tissue sample

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from one of the fins, and then was ready

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with a little vial of preservative

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that I could just pop it right into.

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She wanted to find out if the pups

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were related to known adults, or to each other.

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Lots of people have collected DNA

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from adult great white sharks,

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but collecting DNA from babies can really help us

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to shed light on of other side

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of the great white shark life cycle

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that we really know very little about.

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We can actually find out where

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they are potentially giving birth.

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With most shark species,

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it's common for a single litter of pups

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to have multiple fathers.

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Females use a strategy called multiple paternity,

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which means that a female will actually mate

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with multiple males over the course of one breeding season,

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but instead of using that sperm to fertilize her eggs,

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she will store that sperm from these multiple males

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until she needs it.

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Sperm from different males may mix

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and so those pups that all have the same mom

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will end up with different fathers.

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It's thought that this is because

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most female sharks have little say

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about who they mate with,

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but no one has ever seen great whites mate.

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That would be amazing.

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It would answer a lot of questions.

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Great whites may be different,

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and mate differently from other shark species.

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One thing that makes them different

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is that they're so big.

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They don't tend to aggregate in big groups

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like a lot of smaller sharks.

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Creating a family tree could help

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to understand the mysterious life cycle of this species

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and ultimately help to protect them.

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If we can identify baby sharks

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and possibly connect them to an adult population,

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we can actually make a case for

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protecting the entirety of that shark's range,

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from adulthood to infancy and back again.

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In her Florida lab, Toby used the fingerprint

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technique to compare the Baja babies' DNA samples

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to an extensive database of adult great white shark DNA.

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DNA fingerprinting is using little stretches of DNA

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to compare individuals with a great degree of certainty,

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and it's exactly the same method that crime labs use

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to catch murderers, except that we are using shark DNA.

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She personally took 12 samples

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from the baby sharks and compared them

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to a healthy database of adult white sharks.

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Scientists have been getting DNA

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from Guadalupe's adult sharks for decades.

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Great whites can live as long as humans.

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The estimate that we have right now

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is they could live as many as 70 to 100 years,

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so they live as long as most people,

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but that might actually be an underestimate.

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Females don't reach maturity

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until they're about 16 years old,

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and then they'll give birth to two to 15 pups

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about every three to four years.

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A great white pregnancy is more than

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twice as long as a human's,

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likely 20 months or longer.

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So they don't reproduce very quickly,

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they grow fairly slowly, and they live a long time,

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which actually makes them a lot more similar

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to mammals than to other kinds of fish.

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Toby hoped to find matches between

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the Baja pups and the known females from Guadalupe Island.

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We were really hoping that we would see

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an immediate connection with one of the adults

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at Guadalupe because Guadalupe is fairly close

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to this nursery site, so that was kind of the first thing

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that I went to look for.

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The analysis was disappointing.

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It was really interesting when we saw

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that the pups that we were sampling,

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they weren't all just this one size of brand new baby

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that had just been born that past year.

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There was actually a mix of really new baby sharks

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and some of the older individuals probably from

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the last year or two litters that had grown up

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a little bit but still hadn't left that nursery area.

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As she pushed forward,

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she discovered something completely unexpected.

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We found multiple pairs of siblings,

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specifically we found one brother/brother pair

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and another sister/brother pair, full siblings,

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but some of them were older than the others.

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So what we concluded from that is that

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even though these sharks were brother and sister,

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they'd been born to the same mom

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and the same dad in different litters.

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Not just the same mother,

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the same father too.

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What's really interesting about that to me

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is that that male and that specific female

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mated with each other more than once.

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Wherever the parent sharks came from,

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they seem to have established a connection,

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and while great whites aren't traditional parents,

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mother sharks do what they can to protect their young.

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What they do is they give birth in a place

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where the babies will either be born into

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or swim into a nursery habitat that is relatively shallow

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and protected from really large predators.

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(tense music)

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Female great whites don't stay close

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to their pups after giving birth

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because the massive mothers need massive prey

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after delivering at least 750 pounds of babies.

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Once the last pup is born, they're off to find food fast.

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But they do their very best to ensure

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that their babies have a sanctuary where they can grow,

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find food, and be safe from predators until they're bigger.

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Great white sharks are intelligent.

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They have a long time to get to know their environment.

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They've not only had hundreds of millions of years

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of evolution, but an individual from this species

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can live to see potentially generations

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of its own offspring join that same population.

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From this revolutionary genetic study,

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it does seem that siblings may stick close to each other,

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possibly for many years.

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It's part of their survival strategy,

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as they perfect their hunting techniques.

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Great white sharks as an apex predator

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are in charge of keeping the other levels of animals

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in the environment healthy by weeding out the sick

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or the weak, the ones that shouldn't be reproducing.

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These important and misunderstood predators

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have even more sophisticated strategies for healing wounds

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and even fighting cancer.

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A new white shark breakthrough might ultimately benefit us.

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This genetic study reveals great white superpowers.

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Multiple scientists and organizations teamed up

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to sequence the great white shark genome

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for the very first time.

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Great white sharks have a huge genome compared to humans.

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They have almost twice as many chromosomes as we do,

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and what that means is they don't necessarily have

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more genes than we do, but they have different numbers

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of copies of those genes.

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So where we may have one or two genes

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coding for, say, an antibody in our immune system,

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sharks won't just have one copy of that immune system gene,

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they may have 10.

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(mysterious music)

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Sharks have survived for roughly

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450 million years, through all of Earth's mass extinctions,

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and in the 16 million years great whites have been around,

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they've perfected some amazing biology.

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The scientists found genes that play a role

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in DNA repair and damage response,

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which could explain how these sharks grow to be so big

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without the same occurrence of cancer that we have.

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One of the things that investigators

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who recently sequenced the great white shark genome found

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was that a lot of extra copies have to do with

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wound healing and in particular, clotting factors.

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The genome of these sharks may be why

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they are so effective at being a survivor in the ocean.

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This healing power that these sharks have

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is definitely been one of the keys to their survival.

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It's almost like a great white shark superpower,

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like Wolverine in the X-Men.

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It may also lead to breakthroughs in medicine.

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A lot of our genome evolved from the shark genome,

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including a lot of our human immune system.

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(dramatic music)

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This amazing immune system can not just tell us

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how sharks survive, but potentially can help us

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gain insight into what it means for our own human survival.

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(mysterious music)