The first crocodile-crocodile: the scientist who turned a chicken into a crocodile in the laboratory

Since the days of Aristotle, humans have tried to understand the plan of creation and formation of the embryo

More than two thousand years ago, the Greek philosopher Aristotle started an innovative and unusual experiment. He broke open a hen's egg the first day after it was laid, and scanned its contents for an embryo. He found nothing, except a thin, fleshy strip that looked nothing like a chick. Aristotle repeated the procedure with another egg, this time two days old, and then a three-day, four-day egg, and so on. With this method, Aristotle was able to trace the formation of the chick inside the egg, and recorded how the thin band of cells slowly and miraculously changed into a completely perfect bird. The last remaining egg, on the 21st day, Aristotle no longer had to break. The chick hatched from her on its own.

Since the days of Aristotle, humans have tried to understand the plan of creation and formation of the embryo. "This is similar to a block of iron that becomes the space shuttle." Miroslav Holov said twenty years ago. Indeed, within a few weeks a single cell - the fertilized egg - succeeds in turning into a perfect chick, from beak to feather.

As humans, we are bound to always ask and wonder: What if we could play with the plan of creation? If we understood the body's programming language, which causes an embryo to become a chick or a human, what hybrid creatures could we bring into the world? In the last year, a preliminary answer was received with the creation in the laboratory of the 'taningulat' - a chick with a snout similar to that of a crocodile - and this with very simple means: a small piece of gelatin soaked in a substance called a 'growth factor'.

The growth factors are the substances that guide the creation of the fetal organs. The fetal cells create different growth factors, and these spread all over the body and are absorbed by other cells. In this way, the growth factors are used as a type of words and sentences in the programming language of the developing embryo. Cells that receive BMP-2 growth factor, for example, know that they must change and form bone tissue instead. Cells that receive a growth factor called retinoic acid know that they must change and form nerve tissue or muscle tissue, depending on the amount of retinoic acid they sense around them. If we think of each individual growth factor as a single word, then a combination of several growth factors within the body creates complete sentences and directs each and every cell to create the right tissue in the right place.

Growth factors play a critical part in determining the final shape of the body. They determine, among other things, whether the face of the chick embryo will be shaped into the shape of a crocodile's long mouth, or into the shape of a chicken's beak. In the crocodile embryo, the face develops two separate bones that become an elongated mouth, as a result of the activity of two critical growth factors called 'sonic hedgehog' and 'fibroblastic growth factor 8'. These growth factors appear on the sides of the face of the crocodile embryo, and cause the bones to develop separately.

The pattern of development in the chick is clearly different. The same growth factors work for him too, but they are expressed both on the sides of the face and in the center of the face. As a result of their effect on the cells in the area, the two original bones unite and become one stable bone - the loa is the basis for the origin of birds.

Here the question arises: what would happen if we could control the growth factors and cause them to manifest only in the places where we wanted? Could we sculpt the chick embryo as plasticine in the hand of the creator? To design new and unique forms of life? The challenge of playing God is one that is hard to resist, but this is not just Promethean desire. Many children suffer from congenital defects in the face and body, caused as a result of incorrect distribution of growth factors during fetal growth. If we understand how to control these factors more effectively and safely, we may be able to cure those children even at the stage when they are formed inside the womb.

Biologist Erhat Abzanov decided to pick up the gauntlet and play the god of chicks. He developed a gel containing substances that paralyze the growth factors. These substances adhere to specific growth factors and prevent them from affecting the body. He cut a small hole in the shell of chick eggs, and implanted the gel in the central area of ​​the developing embryo's face. The growth factors in the center of the face became paralyzed - and the chicks developed an elongated mouth resembling that of a crocodile and consisting of two separate bones, instead of a complete beak. The results of his research were presented last month at a meeting at Jackson Laboratories in Maine.

deterrent? Scary? It doesn't have to be that way. Abzanov just turned the dials of evolution backwards. Birds evolved from crocodile-like reptiles, and the growth factors that shaped the faces of dinosaurs are the same growth factors that shape the faces of birds today. The difference is mainly in the location of the growth factors in the facial area.

This means that Abzanov did no more (or less) than undo some of the steps that evolution and natural selection imposed on birds. And he is neither the first nor the last. Other scientists are currently working on deciphering the mechanisms that are responsible for the lengthening of the tail in the chicken embryo, or for the growth of teeth instead of a smooth beak. The success is still partial, but there is a real effort to reproduce the evolution that the chickens went through in the last millions of years, and to return them in the laboratory to the state of maniraptora - small dinosaurs that were the ancestors of the birds alive today.

And what about the regulation and ethics laws? These do not prevent Abzanov's experiments, but they prohibit him from allowing the reshaped chicks to emerge from the eggs. Like Aristotle, Abzanov also had to break the eggs in the days before the chicks hatched, and see how successful his handiwork was.

As with any technology that has potential, this too can be frightening on the one hand - but uplift the spirit and opinion on the other. If we succeed in gaining control of the reins of the body of the fetus, and if we succeed in deciphering all the secrets of the growth factors, then we will have a powerful tool in our hands to create animals that can serve man better. In the short term we may choose to design particularly muscular calves endowed with plenty of meat, or cows with ten or more udders. In the most far-reaching visions one can dream of a conscious creation of animal allies endowed with larger minds and capable of developing basic intelligence.

The technology could also be used to heal human embryos while still in the womb. No more cleft-tongued children who have difficulty speaking will be born. Cyclops - those rare embryonic cases in which the two eyes merge into one eye in the center of the face as a result of a disruption in the activity of the growth factors - will be corrected in the first stages of their development. This technology could also help some of the dwarfism phenomena, in which the bones of the limbs do not lengthen... you guessed it right - again due to a disturbance in the growth factors.

It cannot be denied that this is a powerful force, which can be directed to various purposes. The people of science and morality are also beginning to understand how much the science of biology can change the character of man and the entire world in the coming decades. In the coming year, the European Union is launching a large-scale research project that will try to determine the limits of research and ethics in the field of synthetic biology, and it is possible that the Interdisciplinary Center for Analysis and Technological Forecasting at Tel Aviv University will also participate in the project (under whose wings I have the honor and privilege) and will represent the positions of the State of Israel, About the religious people and the morality in it. Together, as part of a project in which many countries from around the world will participate, we may decide what life will look like in the next generation.

If only we had the wisdom to make the right decisions.

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