Interviews

Genetics

Lynn Margulis, profeessor at the University of Massachusetts

"We all have microbial ancestors"

The evolution theory, even though mostly accepted, can still not be considered definitely closed. Lynn Margulis (Boston, 1938), recognized worldwide for her contributions towards the knowledge of the origin of the cell and for her theory of serial endosymbiosis, maintains open the front of speciation by symbiogenesis, oposed in part to Darwinist dogma, and especially Neo-Darwinism. “We have proved three quarters of our theory”, sustains the prestigious and controversial scientist, who is still active as professor of the Department of Geosciences of the University of Massachusetts.

Xavier Pujol Gebellí | 1 september 2009

In 1970 the first edition of the Origin of Eukaryotic Cells was brought to light. With it the theory of symbiogenesis was born, even though it happened against the flow.
It is true that it was against the flow, even though it generated much greater rejection in my country than in Europe. Maybe because of cultural tradition.

"If I am right, speciation is intimately linked by steps through symbiogenesis"
Lynn Margulis

Even so, in all this time the theory has evolved to the point that it starts, at last, to be accepted. Nearly 40 years have passed.
The theory is based on four parts of which three have already been demonstrated. Specifically, those that talk about the origin of the nuclear cytoskeleton, of the plastids and mitochondrias. Now we are going to demonstrate the forth one.

Let us rewind if you don’t mind.
When I started in evolution one talked of the totipotent origin. In the genealogical tree, it emerged from one point and one advanced through differentiation. Time has shown that trees based on this principle are erroneous. The knowledge of fossils has allowed us to discover that it is not all about a gradual process. Darwin himself said that if evolution is not gradual, its theory is totally wrong.

However it is not totally wrong. Incomplete, maybe.
Right, its theory is not wrong, but it also is not gradual. Also there is no totipotent ancestor either. What one finds is fusion and symbiogenesis spread through the whole genealogical tree. From there we can define the bacteriological cell as a life unit. Therefore, we all have microbial ancestors.

But very little is known of the connection between microbial and pluricellular organisms.
Less than 80% of this connection is known. And what we do know has to do with the last steps of evolution.

You mentioned that there is still a fourth battle to be won. How is that going?
We are working on the origin of the structure of microtubules that govern the movement of cilia. Until now one has never taken into account that these organelles could signify something more.

Would you be able to close the cycle with this?
I sincerely think so. And incidentally, to pay tribute to the first one who spoke of symbiogenesis, the Russian Boris Mihailovich Kozo-Polyansky.

What was his merit?
In 1926, 30 years before his death, he wrote the book Symbiogenesis, a new principle for evolution. In his text he conceptualizes with examples the theory of symbiogenesis and he distinguishes already between prokaryotes and eukaryotes. Its predecessors, which already encourage this theory, rejected Darwin. But Kozo-Polyansky did not. He claimed that the innovation in evolution emerged from the symbiogenesis. And he added that the associations were governed by natural selection.

But now, I insist, there is an international consensus about the validity of your ideas.
My theory has been rejected several times. But it is true. Today everybody accepts that mitochondria come from bacteria and the plastids of green and blue algae. The idea is perfectly compatible with how we see life on the surface of earth coming from the same trunk. This is Darwinism and molecular biology has been in charge of showing this.

One can not go from one species to another simply because of an accumulation of random errorsAnd where is the problem?
When one paints a tree what we see is simply diversification, ramification. But not everything is random mutation; one can not go from one species to another simply by an accumulation of random errors.

Therefore, we are saying that symbiogenesis and natural selection are the clue of evolution and, particularly, of speciation.
If I am right, speciation is intimately linked by steps through symbiogenesis. It’s what we call acquisition of genomes. This concept is demonstrated completely when we refer to the origin of the eukaryotic cell. Two cockroaches belong to the same species when the integrated genomes (their own and that of the symbiotic) have the same components.

That is, the biological principle is fulfilled which says that one plus one is one.
Well yes. And what is more important is that there are no lost links, each step has left descendants. What happens is that in order to find them one has to go to unconventional places. For example, termite intestines or sulphurous sludge of the Black Sea.

And then there is the fourth part.
It’s the one that explains mortality, but we still have not been able to prove it. Even so, we have resolved each step; we have found the correct spirochetes for each one, so that we can talk about a common ancestor for the microtubules and ciliated spirochetes.

But one has to find the adequate examples, establish a relationship.
The genomes of symbionts of venereal diseases, like syphilis, have about one thousand genes. One could say that they have lost 4,000 but, in reality, they are using them from the individual that they infect.

Creationism is a cultural madness

Your theory about symbiogenesis has always been very controversial, even socially.
It is a purely mental question. 57% of Americans think that science is written in the bible telling the history of humanity.

Is it worth asking you what you think of Creationism?
It’s a cultural madness. And also a danger, because behind it lies absolute ignorance. As theory, it blocks the entrance to logic and evidence, something which for a scientist is essential.

There are many though who insist on it.
One thing is to discuss about facts and scientific evidences and another about faith and religion, when it is not morale positions or politics. In the United States one renounced too often the debate of ideas. Fortunately, Europe is more tolerant on this regard.

Is it for this reason that you have also put into doubt what has been said about AIDS?
Since Robert Gallo published his results about AIDS, I have not been able to find any publication that proves satisfactorily that HIV is the causing agent of the disease. What we see is that a huge variability exists and that there is no precise identification of the virus. Of course there is some correlation, because tests detect the virus, because it is there, but nobody has shown yet that it is the causal reason.

Your doubts, and those of your colleagues, have generated a rejection that is hard to bear.
It can be ignored, but it is difficult to resist. Someone is making a lot of money thanks to this disease.

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3 comments

jorge cuellar 25/01/2011
Saludos Xavier Pujol. He buscado sin éxito el Email y teléfono de Lynn Margulis para invitarla a un seminario en Bolivia este año y quiero pedir tu ayuda para comunicarme con Ella. ¿Podrías ayudarme? Gracias por atenderme. Jorge

Alberto Cáceres Benavides 31/03/2010
Realmente este es el lenguaje con el que se debe hablar en Ciencia,si los lectores se han dado cuenta, la Dra. Lynn Margulis emplea muy bien la epistemología, la lógica y la eurística, pilares fundamentales del método científico. Mis más sinceras felicitaciones a esta gran pionera de la Ciencia.

Eva 15/10/2009
Esta mujer es una visionaria, hace años que debieron darle el Nobel!

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