First Human -Search of Adam

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A SEARCH FOR THE FIRST HUMAN

For many of us, the word "genetics" conjures vague thoughts of disease, the human genome, and genetic engineering.

Birth of Adam by Machael Angelo

Spencer Wells thought "genetics" and forged a unique career that combines his love for history with his passion for biology. A geneticist, adventurer, author, filmmaker, and historian—the man adds new dimension to the term multi-tasking—he is using the cutting-edge of technology to explore human history.

He has traveled the world, collecting blood samples from people of far-flung cultures: Aborigines in Australia, the Chukchi tundra dwellers of Siberia, farmers in the hills of Afghanistan, and nomads in the deserts of Africa. By studying the DNA of modern humans, he seeks to learn who we are, where we traveled to populate the world, and how closely we are all related.

"Each drop of blood is essentially a historical document," Wells said. "Our DNA tells the story of the journey of our species."

New DNA studies suggest that all humans descended from a single African ancestor who lived some 60,000 years ago. To uncover the paths that lead from him to every living human, the National Geographic Society launched the Genographic Project, headed by Spencer Wells. The quest for "Adam" is the subject of a new television documentary that airs on the National Geographic Channel in the U.S. this Sunday.

The project is a five-year endeavor undertaken as a partnership between IBM and National Geographic. It will combine population genetics and molecular biology to trace the migration of humans from the time we first left Africa, 50,000 to 60,000 years ago, to the places where we live today.

Ten research centers around the world have received funding from the Waitt Family Foundation to collect and analyze blood samples from indigenous populations (such as aboriginal groups), many in remote areas. The Genographic Project hopes to collect more than a hundred thousand DNA samples to create the largest gene bank in the world. Members of the public are also being invited to participate.

"Our DNA tells a fascinating story of the human journey: how we are all related and how our ancestors got to where we are today," Wells said. "This project will show us some of the routes early humans followed to populate the globe and paint a picture of the genetic tapestry that connects us all."

Tracing Human History

"As often happens in science," said Wells, "technology has opened up a field to new ways of answering old questions—often providing startling answers."

One of the old questions that intrigued Wells was the question of human origins. Whether early humans evolved in Africa or elsewhere, when they began outward migration, and where they went, are issues that have been argued among archaeologists, anthropologists, and evolutionary biologists for decades.

By analyzing genetic changes in the Y-chromosome of people in all regions of the world, Wells and colleagues concluded that all humans alive today are descended from a single African man.

"We're all effectively cousins, separated by 2,000 generations," he said.

In his book, The Journey of Man: A Genetic Odyssey, Wells describes the exodus from Africa that began around 60,000 years ago, and the path we took to populate the world.

Following the southern coastline of Asia, the first early travelers crossed about 250 kilometers [155 miles] of sea, and colonized Australia by around 50,000 years ago. The Aborigines of Australia, Wells says, are the descendants of the first wave of migration out of Africa.

A second wave left Africa around 45,000 years ago and settled in the Middle East, with smaller groups going off to India, northern China, and southern China. As the glaciers of the Ice Age began to retreat around 40,000 years ago and temperatures warmed up, humans moved into Central Asia and multiplied quickly.

Small groups left Central Asia around 35,000 years ago for Europe. Around 20,000 years ago, another small group of Central Asians moved farther north, into Siberia and the Arctic Circle.

He and his colleagues' paper, published in the September 2003 issue of the American Journal of Human Genetics, added evidence to the debate on the peopling of the Americas. The earliest archaeological evidence of human habitation in North America dates to 11,500 radiocarbon years old. Artifacts at a site in Monte Verde, Chile, are in the 12,500-year-old range. However, there are scientists who believe there is some linguistic and archaeological evidence suggesting the possibility that people may have arrived as much as 30,000 years ago.

Mutations in the Y-chromosome of populations in North and South America put an upper limit on human arrival at somewhere between 18,000 to 15,000 years ago. "I would put the number at closer to 15,000," said Wells.

Legacy of Genghis Khan

In another study that looked at blood samples collected over a period of ten years from more than 40 populations living in and around the former Mongol empire of Genghis Khan, Wells and colleagues found that nearly 8 percent of the men living in the region carry nearly identical Y-chromosomes. That translates to roughly 16 million descendants living today.

Archaeological finds and texts describing the history and culture of the region provide some insight into how this one lineage could be so successful, said Wells.

Khan's empire at the time of his death extended across Asia. His military conquests frequently entailed the wholesale slaughter of the vanquished, wiping out many populations. Contemporary documents report that after a conquest, looting, pillaging, and rape were the spoils of war for all soldiers, but that Khan got first pick of the beautiful women. In addition, his male descendants were markedly prolific. They extended the empire and maintained power in the region for several hundred years, in a culture in which harems and concubines were the norm. Khan's eldest son is reported to have had 40 sons. His grandson, Kublai Khan, had 22 legitimate sons, and was said to add 30 virgins to his harem each year.

"This is a clear example that culture plays a very big role in patterns of genetic variation and diversity in human populations," said Wells.

Lost Empires

In addition to a general passion for history, Wells has an abiding interest in lost empires. One of his current projects involves trying to track down the Phoenicians, a civilization that extended from roughly 3000 B.C. to 332 B.C.

"There's remarkably little archaeological evidence of them, and yet they were the dominant culture of the time," said Wells. "Egyptian texts starting from about 1200 B.C. talk about marauding warriors arriving from the sea, yet we really have no idea who they were or where they came from and where they went."

The Phoenicians were a seafaring people who settled a number of independent city-states around the Mediterranean in modern-day countries Syria, Lebanon, Israel, Tunisia, Greece, and Spain. United by a common language, their alphabet became the prototype for the Greek and Roman alphabets; they were the first people to circumnavigate Africa, and may even have reached America.

But where did they come from and where did they go? For that we'll have to wait for the next installment of Spencer Wells' exploration.

Even if people were not created, but evolved, shouldn’t there be a First Human? Who was this person? And when did he/she appear?

Evolution of Human Race

It sounds like a natural question, right? My parents are human... and my grandparents are also human...

and my grandparents’ parents are human, too... But if we go back in time like this, when does the chain

of our ancestors end? If we were created, as for example the Bible says, then of course the chain ends at

our creation point. But suppose for a moment that we were not created at a point in time as the Bible tells

us, but evolved rather gradually, as science tells us — then what? The chain can’t go backwards forever,

because we know there were no human beings, for example, 1 million years ago. So? Doesn’t there have

to be a First Human even in the case of evolution, a pair perhaps — an “Adam” and an “Eve” — who

became the progenitors of our kind? Doesn’t the biblical story have to be true anyway?Some readers

who have read this other page of mine, on the origins of life, have contacted me asking the above question.

In that page I state that there was no first living being, and I try to explain why. Nonetheless, some readers

disagree, and argue for the creation of the First Human even under the assumption of evolution, as I just

explained in the previous paragraph. They see the conclusion as necessarily following by common sense

and pure logic. I would like to show in the present page how it can be logically possible that there was

no First Human. The reasoning is simple, but we need an analogy to make it easier to understand.

Let’s think about something related: the evolution of a language instead of the evolution of humans. Let’s

use a particular language as an example: the evolution of Greek, from the ancient, to the modern language.

(Don’t worry, you don’t need to know a single word of that language to understand this analogy,

guaranteed!

) I’ll tell you how Greek evolved from ancient to modern, without ever having a “first

modern Greek speaker”. What we’ll learn about Greek is true for every other language that evolved from

an older to a later stage (including English, for example), but I prefer Greek because I am more familiar

with the evolution facts of that language, and so I will not make false statements. But the point is that, not

only it doesn’t matter which language we use as example, but also the analogy carries over to what we are

interested at: just as there was no first speaker of a modern language, there was no First Human either. And

the analogy is true even in some of its details! Let’s see first what happened to speakers of Greek.

Add caption

Look at the figure above. Time runs from left to right. The green color is the time when speakers of Greek

were speaking the ancient language, and the blue color is for speakers of the modern language.

Underneath the colored band I drew a large number of very short vertical lines, each of which is supposed

to represent one individual. A single line is one person, and the line to its left is one of this person’s parents,

whereas the line to its right is one of this person’s children. There should be many more lines, actually, but

there is not enough horizontal space to make the drawing realistic. (Other things are not realistic either, such

as the lengths of the ancient and modern stages — but realism is not necessary here.)Now, let’s see what

we have. Each person’s “color” corresponds to the particular version of Greek that the person was speaking.

The difference between colors shows how different the versions were. For example, “very green” means

“typical ancient Greek”, and “very blue” means “typical modern Greek”. Somewhere in-between there is

a region where the language changes. The change is smooth, but also somewhat sudden, if we look at the

overall picture. Indeed, since around 300 BC, after Alexander’s death (that’s Alexander III the Great, king

of Macedon), until around a couple of centuries after Christ, the change was complete. The historical reasons

for the change do not concern us here. What concerns us is the color. Notice this property of the color:

Every parent has a color which is very similar to the color of his/her children. Indeed, from parent toChild,

the difference seems imperceptible. In language terms, every parent speaks almost the same language like

their children. There is some difference, but it is so imperceptible that neither the parent nor the child notice it.

(It could be a few words with a different meaning, some new syntactic structure that the child uses, some

imperceptible difference in pronouncing a vowel, and so on.) As a result, they can communicate with each

other perfectly: the parent understands perfectly the child, and the child understands perfectly the parent.

But now look what happens if we take an ancestor-descendant pair that do not have an immediate parent-child

relationship. How much they could understand each other (if they had lived at the same time) depends on

how much they differ in color; not on how distant they were in time. For example, we can take two ancient

people, both in the very green area on the left, but differing by several centuries from each other — let’s say

800 years. These two people would understand each other, if they could somehow miraculously be brought

together. But if we take a pair where the ancestor is from around 300 BC, and the descendant from around

200 AD (making a difference of 500 years), these two people would not be able to communicate (or, in reality,

the communication would be extremely limited).

Is there any point in time that we can single out and say, “There! That’s when the first speaker of modern

Greek appeared”? Of course not. There is a smooth change, not an abrupt appearance of the first modern

Greek speaker. But even though every parent can communicate with their children (and with their grandchildren,

clearly), still, the change within those centuries is such that the ancient speaker would not be able to communicate

with the modern one, if they could be brought together in time.

Exactly the same idea can be carried over to the notion of change from our ancestor species Homo erectus

(that corresponds to “ancient Greek”) to our own species, Homo sapiens (that corresponds to “modern Greek”).

Let’s take a look at the following figure.

Is anything different between this figure and the previous? Not really. Only the terms have been changed. And

the important points in our analogy are the following:

What was previously language, now corresponds to the DNA of an individual;

and the ability to communicate between two individuals corresponds to

the ability to mate and produce fertile children.

So, if we take any two individuals from among “our kind”, Homo sapiens, which is the clear red region, no matter

how distant in time, these two individuals would be able to produce fertile children after mating (assuming they were

a man and a woman), because their DNA’s would be sufficiently similar. The same thing would happen if we took

two individuals of our ancestor species, Homo erectus, from the clear magenta region in the figure. Again, the

DNA’s of these two individuals, no matter how distant in time, would be sufficiently similar to allow the birth of

fertile children. That’s why we say these two belong to the same species, H. erectus, and those two belong to

another species, H. sapiens. But if we take one “purple” and one “red” individual, their DNA’s would be different

enough to not allow fertile children to be born. It could be that the chances to succeed in having a healthy child

would be nearly zero (say, one in a million). Or, that sometimes children would be born, but those children would

be unable to have children of their own, so they would be sterile, “dead ends” as far as propagation of genes is

concerned.Nonetheless, the magenta region does not change sharply to red, but gradually. There is never any

“First Red” individual. If we take any two opposite-sex individuals that belong to succesive generations (but not

to the same family obviously, avoiding incest), these two individuals (one from the parent’s generation and the other

from the child’s generation) would be able to mate and produce fertile children. They would belong to the “same

kind”, even if they were taken from the transitional time of around 200,000 to 150,000 years ago, because their

DNA’s would be sufficiently close.

How do we know all this? How sure are scientists that the above is true? Have we ever examined the DNA of

a H. erectus, and compared it with the DNA of a modern human?

No, no one has retrieved DNA from fossil bones as old as those of H. erectus. The oldest DNA that has been

retrieved at the time this text was written (ca. 2005) is a few tens of thousand years old. But paleoanthropologist

s (scientists who study the origins of the human kind) examine fossils, and are experienced enough to tell with

some confidence when a skeleton should belong to one species, and when to another. In reality, we will be nearly

100% certain only when we obtain the DNA of a H. erectus individual, and this will take time, because the older

the fossil the more improbable it is that the DNA has been preserved somewhere. But it is not impossible to find

it, somewhere on this planet. Perhaps deep frozen under the vast unexplored ice sheets of Siberia (if H. erectus

ever reached there).

But suppose that we find such a DNA molecule, and after we compare it with a modern DNA molecule we realize

— to our surprise — that in fact the two DNA’s are similar enough to qualify as “same species”: the two individual

s would in principle be able to have fertile children after mating. Would this discovery demolish the explanation

presented in the previous paragraphs, about the nonexistence of a “First Human”?

Not at all. Such a discovery would simply push the species-distinction era further back in time. All right, so it would

not be what we call H. erectus the species of which we would have the honor to be the descendants. We would be

the same species with them, in that case. So? There would be another species, further back in time, that would have

sufficiently different DNA to disallow mating and production of offspring with “us”. But still the change between that

species and the erectus-sapiens species would be gradual-and-yet-abrupt, as the figure with the magenta and red

colors depicts it. And so, still there would be no “First Human”.

This notion of “gradual-and-yet-abrupt” change, by the way, is a hard one to grasp, because the words sound

self-contradictory: is it gradual, or is it abrupt? But I think the colored figures, above, depict in a nice way how the

change can be both gradual and abrupt, without any contradiction:

The change is gradual because between any two successive generations the difference (in DNA, in language structure) is minimal; so, successive generations can “communicate” (pass on their genes, mutually understand their ideas). Thus, the change is gradual when we take the magnifying glass and look at it from up close.
But the change is also abrupt when viewed at a larger scale: for a very long time, there is almost no change at all (same species, same language), which is called stasis in biology; but within a very short period of time (“short” relatively speaking), changes occur and accumulate “fast”, and we arrive at a different “kind” (another species, another language). The change is abrupt when we zoom out and look at the overall picture from afar, taking a bird-eye view.

Naturally, the previous discussion is true for any two species that have an immediate ancestor-descendant relationship; it is not confined to the human ancestry case.

Though not relevant to the “First Human” question, for the benefit of some readers who objected to the above, I feel I should also mention the following related issues.Some people feel uncomfortable when reading these things. One (unfortunately still common) reaction is: “But does that mean we evolved from the chimpanzees?”

No, the chimps aren’t our ancestors; but we share a common ancestor with the chimps. So, we are like “cousins” with them. But then, so what? We also share a common ancestor with the dogs and cats; and with horses; and with birds; and with fish; and with plants; and with bacteria; and with every living being on this planet. What’s the big deal with poor chimps?

In truth, there is something special between us and chimps. It is that of all living beings on Earth, chimps have a DNA structure which is most similar to ours. This is a hard fact, like “the Earth is round”; it cannot be disputed: you take the chimp-DNA molecule in the lab (an average of some living individuals), and the modern human DNA (again, an average), you compare them, and find some differences. If you do this with any other living being on Earth, you’ll find that the chimp DNA has the fewest differences from our DNA. That’s all that there is to it. And that’s why we look more similar to chimps than to rhinos.

And if you continue your DNA-explorations, you’ll find that the next-most-similar DNA to ours after the chimp (the two species of chimps, actually: the common and the bonobo), is the one of the gorilla. And after the gorilla follows the orangutan. And then the gibbon, the “lesser ape”. And then, more distant, are the DNA’s of monkeys and other primates. But still, all these DNA’s are closer to our DNA than, say, the elephant’s DNA.

All these are indisputable facts. And the theory of evolution explains these facts. It says, for example, that our common ancestor with the chimps lived more recently than our common ancestor with the gorilla. It is as if we are first cousins with the chimps, but second cousins with the gorillas (and third cousins with the orangutans, and so on). If some readers feel shame that we have such relatives, I would say, I feel more proud of being related to the peaceful bonobo chimps, rather than to some people such as Hitler and Pol Pot. What about you?

Opinions expressed by readers after reading this pageA reader from a discussion group wrote the following (in their forum, the full text can be found here):

Apparently this individual [i.e., I, the author of the present page] is not familiar with the logical fallacy of “false analogy”. He explains, he proves his argument by referring to an analogy. The only problem is that we can prove anything by using an analogy.
In this particular case, an individual can switch between a “old Greek” speaker to a “modern Greek speaker”, and switch back again at pleasure. The barrier between old Greek and modern Greek is easily penetrated. Actors can speak with many different accents and languages.
However, there is a barrier between living and non-living, between a cat and a dog, between a human being and some other creature. That barrier cannot be penetrated at will. I can move back and forth from green to blue, but I cannot move back and forth between human and non-human at will (except for science fiction, of course == “The Human Fly”, and other such nonsense.
He bases his argument, the foundation of his argument is an analogy which is fundamentally flawed.

The above reader’s view is wrong on a couple of counts:

1. I don’t attempt to “prove” anything with this analogy. Firstly, real proofs do not exist in any domain other than mathematics. Every use of the word “proof” elsewhere is sloppy. But setting sloppy language aside, and replacing “he proves” (in the first quoted paragraph, above) by “he brings evidence for”, even this idea is wrong: I don’t attempt to bring evidence for anything. An analogy does not bring evidence; it simply invites the mind to remove its blinders and expand its horizon by making a mapping between an unfamiliar idea or situation, and a hopefully more familiar one. An analogy is a thinking aid, not a proving tool.

2. The above reader’s main point is that mine is a “false analogy”, because there is a barrier (I adopt his terminology) between species (e.g., a cat cannot become a dog, and vice versa), whereas there is no such barrier between speakers of languages such as ancient and modern Greek. This idea is wrong for two reasons:

2a. It is not true that speakers can switch between languages such as ancient and modern Greek. I am talking about native speakers.⁽³⁾ Ancient Greek, as we all know, is a dead language, meaning that there is no native speaker of it alive today. A dead language cannot be revived: we cannot have native speakers of ancient Greek today, no matter which way we try. For to have a native speaker a community of other native speakers is required, and an individual must grow up in that community from a very early age. (There is a “window of opportunity”, well-known in developmental linguistics, available to every mentally normal child, that appears from birth to the early teenage years; a child who is not exposed to a given language during this window of opportunity cannot become a native speaker of that language.) Given that there is no community of speakers speaking ancient Greek, it follows that we cannot have a native speaker of ancient Greek in our times.

2b.Even if the above point (2a) were not true, i.e., even if there were really no barrier between ancient and modern Greek, one must have a sense of which features of an analogy are essential, and which are irrelevant. An analogy is not an isomorphism, forcing every detail to be identical between the two mapped structures. For example, the DNA is propagated by sexual reproduction (at least in the cases of species concerning us here), so a female and a male individual are required; but there is nothing analogous to sexual reproduction in language. On the other hand, a language has a mandatory spoken form and an optional written one, but there is nothing analogous to this in the DNA case. Also, language speakers can be bilinguals or even trilinguals, etc., i.e., native speakers of more than one language, if they grow up in suitable multi-language-speaking environments; but living beings cannot belong to more than one species. All these differences (as well as the purported one suggested by the reader) are irrelevant for the analogy, the essence of which is that just as one does not need to postulate a single initial speaker of a language, so one does not need to postulate a single (or a couple of, male and female) initial ancestor(s) of a species. (Again, this is not a “proof”, or evidence for anything; it is simply a suggestion that it is logically possible to not have a single individual, or couple, as the progenitor of an entire species.)

Other opinions, expressed either in public or in private (by email to me) will be answered here, if in my view they raise some interesting point. The privacy of the opinion holder is guaranteed upon request.

Footnotes (clicking on the number brings back to the text)

1. How do we know this? Because no fossil skeleton or single bone of our kind, Homo sapiens, has been found that is older than around 200,000 years ago.

2. But in case you do happen to be interested in the historical reasons, they are related to Alexander’s conquests. In the centuries after his death, a lot of people in Asia and N. Africa learned to speak Greek. So did the educated among the Romans. Thus, Greek became a “lingua franca”, the international language of those times. However, because it started being spoken not only by native Greeks, but also by “barbarians” (as the Greeks were calling all non-Greeks, but not in the modern derogatory sense), the Greek language was “eroded”. This phenomenon has been repeated many times in history — take, for instance, English and its difference between its modern varieties and the English of Chaucer’s time (1340?-1400). Also, contrary to the modern era, in the ancient times there was no television or radio so as to standardize Greek and let one dialect prevail (e.g., the Attic dialect). Today the so-called “common American” is heard and understood throughout the English-speaking world, thanks to Hollywood and TV series. Back then, however, neither Athens nor any other Greek city had such privileges, so the rest of the Greek speakers eventually brought about the changes that led to the Greek language of the Byzantine times, which are easily understood by modern speakers of Greek.

3. Why the analogy works with native speakers only? Because languages are determined largely by the utterances produced by their native speakers. Non-native speakers can induce changes in a language and cause it to evolve in a catalyst-like fashion, as footnote 2 explains, but they do not determine what the language is. If we include, for example, my ungrammatical Italian as part of the Italian language (because I happen to know a few Italian words and can surmise about how to put them together), and we do this for every non-native speaker of Italian, then the Italian language will lose its character; it will cease to be what it is it will hardly be recognized as Italian.

4. The following thought experiment is possible, however: a number of ancient Greek aficionados gather in a place and form a community. They all know ancient Greek as a second language, i.e., they are not native speakers of it. But they all live in the same locality, marry only with members of their community, and raise their children by speaking to them whatever ancient Greek they know. Modern linguistic theory then predicts that the children raised in this way will become native speakers of ancient Greek (or a close approximation thereof), automatically correcting the non-native errors of their parents. (We have to assume that the parents are very good non-native speakers, otherwise the children might converge to a language that differs substantially from true ancient Greek.) Examples of such a situation come from communities speaking pidgin languages, where children raised within such communities became native speakers of creolized languages.

However still the evolution of Human has unsolved mysteries.