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La EVOLUCIÓN, DEMOSTRADA por los FÓSILES — Transcript

by El Pakozoico · 3,961 words · 623 segments · language en · Watch on YouTube

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0:01Oh, it's funny, hm, the amount of
0:08nonsense that is said on social media.
0:13Misinformation is everywhere and many
0:15times we feel the need to look for
0:17extraordinary things to believe that
0:19our life is more extraordinary than our
0:21day-to-day life. Where does this lead
0:26us? That many times we get carried away
0:29by strange ideas, conspiracy theories
0:38and alternative visions that most of
0:40the time have no evidence to support
0:41them, but that make us feel a special
0:43pleasure. Oh, I've noticed something
0:48that you haven't. Where am I going with
0:50all this? That there is a lot of
0:53skepticism of the bad kind, not the
0:55discarded kind, but the bad kind. There
0:59is a lot of denial of our work, of the
1:01fossil record and one of the things
1:03that is most often said is that the
1:05fossil record denies or contradicts
1:07evolution. And this happens in part
1:11because every time there is a great
1:13paleontological discovery in the news,
1:15in the press, it is sold in a
1:17sensationalist and super-yellow way.
1:20They look for clicks and often say,
1:22well, this reformulates the theory of
1:24evolution. We have to change the
1:28textbooks on human evolution, we have
1:30to tear down our building and rebuild
1:32it because this completely breaks the
1:34mold. I can tell you that 99%of these
1:41findings do not destroy anything or
1:43have to change anything because the
1:45knowledge we have in biology and in
1:47polarology of biological evolution and
1:50the fossil record is so vast and so
1:52complex that all these findings have a
1:54place. I assure you. Today, in order to
2:01tell you how the fossil record and
2:03biological evolution are so
2:04well-contrasted and so well-linked, I
2:06am going to talk to you about a series
2:08of scenarios or a series of predictions
2:10that are generated from biological
2:12evolution through natural selection,
2:14which can be observed directly or their
2:17effects can be observed in the fossil
2:19record. And that's it. Let's get to it.
2:24Come on. Do you remember Darwin? Thanks
3:02to the observations he made on his
3:04voyage around the world on the Beagle,
3:06he realized that current species had
3:08arisen from previous forms, from
3:10previous species, through a process he
3:12called natural selection. At the same
3:15time, another naturalist, Alfred
3:17Russell Wallas, had reached a very
3:20similar conclusion, studying the flora
3:22and fauna of the Amazon and the Malay
3:24Archipelago. And they corresponded;
3:27they sent each other letters, because
3:29that's how communication was back then.
3:31Even when I was little, communication
3:33was like that; now it's very immediate,
3:36the world is crazy. That's how in 1858
3:39Charles Darwin presented a
3:40communication, he made a presentation
3:43of his theory of evolution through
3:45natural selection at the Linnaean
3:47Society of London. And since he had
3:51been corresponding with Wallas and they
3:53both agreed and had reached these
3:55conclusions, he presented this with
3:57Alfred Russell Wallas as co-discoverer
3:59of this, as co-author. Darwin had a lot
4:02of ideas there, which we have to say
4:04was very useful to Wallas because
4:06Darwin had a lot of contacts with all
4:08the naturalists in London, he had a
4:10good relationship with them, let's say
4:12he had more contacts and suddenly
4:14signing Darwin for Wallas was great. So
4:17there, Darwin, wow, you've worked hard,
4:20my God. Although Darwin's presentation
4:25in the Linnaean society didn't have a
4:27great impact because it was a
4:28communication at a conference, to give
4:31you an idea, the following year Darwin
4:33published his book On the Origin of
4:35Species and that was really crazy. It
4:40sparked controversy, it became a trend,
4:42it was crazy and this discovery
4:44revolutionized not only the natural
4:46sciences, but also society; because
4:48until that moment, humanity, humans,
4:51believed that we were a divine and
4:53unique creation, above all other living
4:55beings and above the rest of the
4:57natural world. And with this proposal,
5:04it suddenly turns out that all life
5:06forms are related, including us, and
5:08that therefore we also come from
5:10animals, our ancestors, who were not
5:12divine beings created by anyone. This
5:18was a shock, this was a trauma, this
5:20was a drama. Well, today biological
5:22evolution is already a super-proven
5:24scientific fact. We have
5:26paleontological evidence, zoological,
5:28botanical, geological and molecular
5:31evidence. It is a real process that is
5:35observed, that is studied. Many people
5:38come to me with the idea that it is a
5:40theory, let's see, a scientific theory
5:42to be presented as a scientific theory
5:44has to be based on measured
5:46observations. It is not the theory that
5:48you make up about the end of your
5:50favorite series at the hairdresser's.
5:51That is your theorization, your theory,
5:53call it what you want. A scientific
5:56theory needs observations of phenomena
5:58that have been verified, reported,
6:00measured, quantified in order to
6:02propose it. And furthermore, it is not
6:05evolution that is theorized, but rather
6:07the mechanisms of natural selection to
6:10explain this evolution. Evolution is
6:12real. It is as real as the ground you
6:14walk on, as the air you breathe. Isn't
6:17that clear to you? Anyway, the point is
6:19that to return to talking about the
6:21fossil record, since we have already
6:23talked about the fact that it has these
6:25samples, these demonstrations of the
6:27fossil record, evolution, the fossil
6:28record has limitations, it has little
6:30problems. The biggest problem with the
6:32fossil record is that it is very biased
6:34and that is because all living beings
6:36that live on Earth and have lived on
6:38Earth do not have the same chances of
6:40becoming fossilized. I may not
6:42fossilize, you may. Who's to say? The
6:45point is that an animal that has hard
6:47mineralized parts in its body, such as
6:50us who have bones and teeth, or for
6:52example a mollusk that has a shell, a
6:54carapace, we have more chances of
6:56becoming fossilized than an animal or
6:58plant that does not have hard parts
7:00with minerals, hard mineralized parts.
7:02But between the two, if a mollusk lives
7:04in an aquatic environment, it has a
7:06better chance than I do of becoming
7:08fossilized, because it already lives in
7:10a sedimentary basin where sand or mud
7:12is being deposited at the bottom. And
7:14the moment that poor little animal
7:16passes away, its shell falls to the
7:21bottom and it is practically alone, it
7:23is buried. Well, I have to be buried
7:25and mourned for and things like that in
7:27order to preserve my body for the
7:29future. It is easier for a mollusk.
7:34Even if you are perfectly buried, you
7:36may not see the light of day as a
7:38fossil in thousands or millions of
7:40years, because the sediment in which
7:42you are buried may end up eroding and
7:44disappearing, leaving nothing left of
7:46you. In other words, it is quite a
7:50lottery. Fossilization is a very
7:52complex process and the fossil record
7:55is obviously very biased. There are
7:56things that are preserved, and there
7:58are things that are not. There are
8:00things that favor conservation and
8:02others that are more due to chance. So,
8:05what we paleontologists have to do is
8:07work with what we have and not lament
8:09what we don't have because then we
8:11would spend the day crying. People who
8:16work in paleontology already assume
8:18that the fossil record is biased and
8:20yet, despite the biased nature of the
8:22fossil record, we have a large number
8:24of samples of entire lineages and
8:26transitional forms of these lineages.
8:32What's more, as I was saying, we can
8:34make predictions or models based on
8:36biological evolution through natural
8:38selection and we can test them, see
8:40what there is of them, what there is of
8:42these scenarios or these predictions in
8:44the fossil record. First, according to
8:48biological evolution through natural
8:50selection, organisms have evolved from
8:53simple forms, simple forms. Let's go to
8:56the fossil record. What are the first
8:58fossils like? Simple beings. They are
9:01fossils of unicellular beings. Even the
9:04first macrofossils of something
9:06resembling protoanimals, we could say.
9:10They are very simple, such as the biota
9:13of Diacara, which in fact is still
9:15unclear whether they are protoanimals,
9:17larger protists or what the heck they
9:19are. They are living beings with a
9:24structure, with a simple organization,
9:26so that the fact that life forms come
9:28from simplicity is definitely observed
9:30in the fossil record. Secondly, species
9:34evolve from preexisting varieties. In
9:41fact, we have known about this for
9:43decades, practically since William
9:45Smith spoke of faunal succession and
9:47how different fossils appear in a
9:48similar sequence everywhere, we know
9:50that there have always been preexisting
9:53species. At that time, William Smith
9:57did not know anything about their
9:59relationship, but then Darwin and Walas
10:01came along and things changed. The
10:02interpretation of this sequence of
10:04faunas began to change. What I mean is,
10:08we can choose practically any group of
10:10extant animals, including plants and
10:12all types of organisms, but let's focus
10:14on animals. You can choose any group of
10:20extant animals and find their ancestors
10:22, both in a more recent geological time
10:24and in an increasingly remote
10:26geological time, which allows you to
10:28see from which pre-existing varieties
10:30the current species arose. And from
10:35which other, more ancient varieties do
10:37these pre-existing varieties still
10:39originate? For example, I go for a walk
10:42with Spike in the park and I find
10:44pigeons and I find parrots, current
10:46birds. I could go to the geological
10:48record of the Cenozoic and see
10:50ancestors of modern birds in the fossil
10:52record. What's more, I can go further
10:55down this stratigraphic sequence. I can
10:57go to the Mesozoic, to the era of the
10:59dinosaurs, and I can find primitive
11:00birds with more primitive
11:02characteristics. I can even see
11:03steropod dinosaurs from the group of
11:05maniraaptors that already have
11:07characteristics that these primitive
11:08birds later inherited. And I can even
11:11see the origin of the characteristics
11:13of these theropod dinosaurs. In other,
11:15more primitive dinosaurs, I can go
11:17further and further down the geological
11:19record and even find the ancestors of
11:21dinosaurs. I can find the ancestors of
11:24reptiles, and so on and so forth. We
11:27will always be able to find preexisting
11:29varieties from which later or current
11:31species derive, as Darwin said, the
11:34equals. Third, the greater the
11:37similarity between organisms, the more
11:39closely related they are. This is
11:41something that has been used since the
11:43beginning of natural sciences to group
11:45animals together based on how similar
11:47they are. Only for a long time it was
11:49used to bring order to this chaos that
11:51is the natural world. And for some
11:53years now, it has been known that there
11:55is an underlying kinship there, that it
11:57is because we are related in some way.
12:00Traditionally, we group animals and
12:02plants based on pure similarity.
12:04However, for some years now, since
12:06everything has been studied from an
12:08evolutionary perspective, we have only
12:10looked for similarities that are due to
12:12evolutionary innovations, which we call
12:15apomorphies. For example, we are not
12:17going to use the fact that we have five
12:19fingers on our hands to classify
12:21mammals, or ourselves within mammals,
12:23because all mammals have five fingers
12:25on their hands. There are mammals that
12:27modify this and lose fingers. For
12:30example, horses only have one with
12:32their hoof, but the most common
12:34characteristic is for mammals to have
12:36five fingers, so we are going to use
12:38that as a characteristic to group
12:40mammals. We use what we call
12:43evolutionary innovations or apomorphies
12:45to arrive at these classifications that
12:48are based more on kinship. And it is
12:51interesting that this kinship and these
12:53common characteristics go hand in hand.
12:56We do not find similarities between
12:58characters or animals in a chaotic way,
13:01but rather that, curiously, they make
13:03sense, they make evolutionary sense.
13:06And this is something that is confirmed
13:08not only by the fossil record, but also
13:10by molecular biology. Not only are
13:12closely related species similar in
13:14their anatomy, but they are also more
13:16similar molecularly. Fourth,
13:20interspecific competition can be a
13:22cause of extinction. Okay, here we have
13:25to introduce the concept of background
13:27extinction. Why do we believe that
13:29extinctions always come from
13:31catastrophic events that suddenly wipe
13:33out every living thing? In fact, it is
13:35common to think that, uh, dinosaurs,
13:37all species of dinosaurs appeared in
13:39the middle of the Triassic and
13:41disappeared at the end of the
13:43Cretaceous. Well, no. There have been a
13:47series of lineage changes of species
13:49over 150 million years and the species
13:51that lived in the Cretaceous have
13:52nothing to do with those that lived in
13:55the Triacetic. During this changeover
13:58of species, some disappear and others
14:00emerge, sometimes some are descendants
14:03of each other. This changeover of
14:06species occurs due to a so-called
14:08background extinction. What is the
14:10opposite of mass extinction, which is
14:12the typical extinction that we have in
14:14mind? So any disappearance of a species
14:16in the fossil record is a background
14:18extinction if it only occurs in one
14:20species and only when the disappearance
14:22of several lineages or several species
14:25coincide in time, can we speak of a
14:27more massive extinction, especially
14:29when it is due to fluctuations in the
14:31environment. So, this replacement of
14:34some species by others and of some
14:36lineages by others and that suddenly
14:38leaves an ecological niche empty and
14:40another new species that emerges fills
14:42it. This is constantly observed in the
14:44fossil record. The fossil record is not
14:47the monopoly of a species until a mass
14:49extinction, a meteorite, a volcano or a
14:52supernova comes along and everything
14:54goes to hell. You can't constantly see
14:58this changeover and that changeover and
15:00that background extinction often occurs
15:02due to phenomena like this, it's like
15:04this interest-specific competition.
15:08There is an entire specific competition
15:10between different species that use the
15:12same resources. They fulfill a similar
15:14ecological niche; some species are more
15:17successful than others. There is some
15:20fluctuation in the environment, any
15:22change that changes the situation, and
15:24one species takes the lead: it
15:26overtakes the other and the other one
15:28goes to hell. It is very common. We
15:33have talked about interspecific
15:35competition, now we are going to talk
15:37about intraspecific competition. There
15:39is intraspecific variability and
15:41competition, therefore, between such
15:43diverse individuals within a species
15:45that is a driver of different survival
15:48and therefore of natural selection.
15:50This can also be observed if I go to
15:52Pasadera Spike Park, I see it in
15:54pigeons too. I don't have to look at
15:56whether they are missing more toes on
15:57their feet or if they have more or
15:59fewer stumps. Those are things that
16:01life is a about, right? But if I
16:03only look at the general
16:05characteristics of these pigeons, some
16:07are bigger, others are smaller, more
16:09robust, lighter, with different
16:11colorations in their feathers. Even in
16:15ourselves, in humans, we can see that
16:17we are all different. We vary in
16:21robustness, height, limb length, facial
16:24shape, hair color, and skin color. This
16:28is intraspecific variability, and if we
16:30look at the fossil record, we can
16:32observe it. People who work with
16:35invertebrates have it easier because
16:37they usually have many specimens of
16:39their species, of each of the
16:40invertebrate species they study. Those
16:42of us who study vertebrates have it a
16:44little more complicated. For example, I
16:47only know of two Sillasaurus specimens.
16:49The one from Cañada in Aras de los
16:52Olmos and the one from San Lorenzo in
16:54Riodeva, in Teruel. Two. So, I can't
17:00observe much variability, but the more
17:02specimens are known of species, both
17:04current and fossil, the more specimens
17:06are known, the more striking it is that
17:09there is variability in all species in
17:11the fossil record. In the dinosaurs of
17:15which more specimens have been
17:16recovered, such as Tyrannosaurus,
17:18Allosaurus or Camarasaurus, for example
17:21, variability is observed. In fact,
17:23there is so much variability that there
17:24was even an illustrious person who said
17:26, "Let's see if there are three species
17:28of Tyrannosaurus." I tell you right now
17:30, no. It's a picture. It's a picture.
17:33Sixthly, differential survival will
17:35mean that the fittest will survive and
17:37they are the ones most adapted to their
17:39environment. Well, we can see this in
17:43the fossil record in the sense that we
17:45only see species living, well, living
17:47and leaving their remains in an
17:49environment. They are species that are
17:52adapted to that environment. You study
17:54the fossils that are in a site and a
17:56colleague of yours who is a geologist
17:58studies the characteristics of that
18:00sediment, of that site to reconstruct
18:02the environment in which it was formed
18:04and you see that there is a correlation
18:06. The type of animals and plants that
18:08lived in an environment makes sense.
18:10You go to a different geological
18:12environment with deposits and you will
18:14also see that species in a different
18:16environment, species also have
18:17different adaptations. So adaptation
18:20goes hand in hand with the environment
18:22and you can see it in the fossil record
18:24. It is not chaos and randomness. It
18:27has a meaning and this meaning lies in
18:29the adaptation of species to the
18:30environment in which they live. Finally
18:35, Darwin himself, much to his regret,
18:37was clear that the fossil record was
18:40biased and, in fact, he saw it much
18:42worse than we do, because except for
18:44some mention, such as a mention he made
18:46of Archaeopteryx in later reissues of*
18:48On the Origin of Species*, in general
18:50he himself recognized that there were
18:53not many examples of complete lineages
18:55in the fossil record or of transitional
18:57forms between different life forms that
19:00could support his theory. Luckily, this
19:06has changed, the tables have turned and
19:08we have plenty of examples. The first
19:12example we are going to look at are the
19:14first terrestrial vertebrates, which we
19:16could traditionally call the first
19:18amphibians. We have records of them.
19:20They appeared from sarcopterygian fish,
19:23that is, fish with fleshy fins, such as
19:25coelacanths. Their fins were already
19:29modified to have sedimentary legs with
19:31joints, with little toes that would
19:33have allowed them to rise from the
19:35substrate of the bottom. This is the
19:39case, for example, of Tictalic,
19:41Ichthyostega or Acanthostega that lived
19:43during the Debonian period
19:45approximately 375 million years ago. We
19:48also have the case of synapsids, which
19:50we traditionally called mammal-like
19:52reptiles, which I still like the term
19:54mammal-like reptile, although I must
19:56admit that it is nostalgic, it is
19:57vintage, because in reality we should
19:59talk about synapsids. Well, synapsids
20:02are the entire lineage that includes
20:05mammals and their ancestors. And
20:08basically, you can trace the origin,
20:10the origin of the mammalian lineage,
20:12you can trace it back to the Permian
20:14period, between 290 and 250 million
20:16years ago. It's just the period before
20:18the age of the dinosaurs and right at
20:20the end of that period there was a huge
20:22mass extinction, the biggest one, the
20:24one that almost wiped out our entire
20:26lives. Well, in this Permian period we
20:29find what we traditionally called
20:31mammalian reptiles, what we now call
20:33primitive synapsids, which were very
20:36diverse in the Permian; some made it to
20:38the Tricassian and some of them already
20:40had adaptations that we mammals have
20:42inherited, such as the presence of a
20:44secondary palate, the differentiation
20:46of teeth for different functions, the
20:49fact of having incisors, canines and
20:51molars: they started to have them and
20:53we simply inherited them. Or, for
20:57example, hair. In fact, many of them
21:00already have, or should already have,
21:02whiskers, those little whiskers that
21:05mice, cats, and dogs have. These
21:12whiskers are sensory hairs associated
21:15with nerves with holes in the skull.
21:17This can be seen in many of these
21:19synapsids, so it is possible that they
21:21had hair like the one we have. Some
21:24have more hair than others. Yes. Human
21:27evolution itself is also a case of a
21:29well-documented lineage. Despite the
21:31fact that every time there is a
21:32discovery in the news it is said that
21:34this is revolutionized, turned upside
21:36down, completely changed. Calm down,
21:38gentlemen. The great milestones of
21:40human evolution are more than
21:41documented. How many species there are
21:43in these lineages, how these lineages
21:46have actually coexisted or not, and so
21:48on. These are already topics for debate
21:50, but the great milestones of human
21:52evolution are very well-documented and
21:54proven thanks to the fossil record. We
21:57know that Australopithecus were the
21:59first to stand up, or rather, their
22:01direct ancestors already have evidence
22:04in their anatomy that they could stand
22:06up; therefore, bipedalism came first
22:08and that, after bipedalism, brain size
22:11increased, along with other adaptations
22:13, the development of culture, and the
22:15development of tools. All of that came
22:18later and we know this thanks to the
22:20fossil record, and we have very good
22:22records of all the species of humans
22:24that have ever existed. We know that
22:26human evolution has not been linear,
22:28but rather one of diversification and
22:30that in some cases there has even been
22:33coexistence between different human
22:35species, even hybridization. And
22:37finally, we have the case of primitive
22:39whales, a lineage of adaptation from
22:41one environment to another, right? From
22:43the terrestrial environment to the
22:45aquatic environment. And yet we do not
22:47have many, not many fossils, not many
22:49fossil species, but we do have enough
22:51to know how this process occurred. For
22:54example, we have Pachycetus, which is a
22:57terrestrial mammal in principle, but
22:59which already has adaptations to at
23:00least an amphibious life, adaptations
23:03in its hearing to hear well underwater.
23:05It has pachycetosis, it has very solid,
23:07very dense, very heavy bones that would
23:09help it to hide in the water and be
23:11able to dive. It even has the eyes in
23:14its skull modified to be more upwards,
23:16which is perfect for being able to
23:18observe from the surface of the water.
23:21Then we have intermediate forms such as
23:23Ambulocetus, which has a way of life or
23:25is associated with a way of life
23:27similar to that of an otter, or
23:28fully-fledged whales, fully-fledged
23:30whales, such as Basilosaurus itself,
23:32which, although its name seems to
23:34indicate that it is a dinosaur or a
23:36reptile, it was only named that because
23:38of its similarity; because, obviously,
23:40its skeleton looks a little reptilian,
23:42but it is a whale, a full-fledged whale
23:44in its own right, although it still has
23:46primitive characteristics in its teeth
23:48or in its extremities. So, we can see
23:51how the whale lineage has been, how
23:53they have readapted to the aquatic
23:55environment without any problems. So
23:58yes, we have, uh, so much evidence of
24:00these scenarios that are proposed from,
24:03uh, evolutionary biology. We can
24:07observe these predictions in the fossil
24:09record and we also have increasingly
24:11better recorded, better verified
24:12information about the different
24:14lineages, how the origin and evolution
24:16of each lineage of living beings has
24:18occurred from the very origin of life
24:20to the present. So there you have it.
24:24And that's it, thank you very much for
24:26watching this video, I'm so glad you've
24:28watched it this far. Thank you very
24:29much, especially thanks to all the
24:31people who support my channel through
24:33the usual means, Patreon, members of
24:35the channel on the YouTube platform,
24:37one-off donations or simply by sharing
24:39the video on all your social networks.
24:41Thank you very much, you have earned
24:43heaven, beautiful people. And that's it
24:46, thank you very much and see you in
24:48the next video, okay? Remember, if you
24:50put them in the comments, even if
24:52they're dinosaur emojis, you're helping
24:54me. And if you have any questions or
24:56any topics you want to suggest, put
24:58them in the comments below, it helps me
25:00a lot. Thanks. And now, see you in the
25:03next video. Bye. You didn't say the
25:26magic word.

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This page contains the full transcript of La EVOLUCIÓN, DEMOSTRADA por los FÓSILES by El Pakozoico, generated from the public captions YouTube serves with the video. The transcript has 3,961 words across 623 segments, with the original timestamps preserved so you can click any line to jump to that moment in the embedded player.

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