Breeding Mice Without a Father / Aggression in Monkeys / Early Human Brains
This is SCIENCE IN THE NEWS, in VOA Special English. I'm Bob Doughty. And I'm Sarah Long. On our program this week -- making a mouse with two mothers, no father required.
A monkey society where females teach males to be less aggressive.
And a theory why people have a bigger brain but a smaller mouth than early humans.
There is a mouse in Japan with two mothers and no father. How could this happen? Scientists explain how in the magazine Nature. However, the process they used to create this small animal is not new. It is called parthenogenesis.
Parthenogenesis is development with an unfertilized egg or reproductive cell. Some plants and animals reproduce this way. Among them are a number of fish and birds. Scientists thought mammals had to have an egg from a female and sperm from a male to reproduce.
Tomohiro Kono of Tokyo University of Agriculture led a team of Japanese and Korean scientists. They used only female mice in their experiment. They joined the nucleus of an egg from one mouse with the nucleus of an egg from a second mouse.
They combined a young egg with an older egg. The young egg had not yet gone through an important part of development. Its genes were not yet imprinted. During this process, some genes are ordered to work and others are not.
The imprint depends on whether the gene comes from the mother or the father. Eggs and sperm have similar sets of genes. But the imprint decides which gene in a set should be active and which should not.
The young egg came from a genetically engineered mouse. This mouse was made to lack two genes linked to the growth of a fetus.
Tomohiro Kono says he thinks the young egg acted more like a sperm because of the missing genes. The older egg was already imprinted. It had all the normal genes.
In their experiment, the scientists produced hundreds of embryos. They placed them inside female mice to grow. Only ten live mice, all female, were born. Just one of these survived to grow into an adult.
The scientists named her Kaguya, after a princess in a Japanese story. Kaguya is now more than a year old. She has already had babies through the way mice normally reproduce.
The team says the results of the experiment suggest that imprinting with genes from the father prevents parthenogenesis. This would make sure that the father has a part in the development.
Scientists say this experiment should not worry men. They say parthenogenesis will not replace them anytime soon. But experts in genetics and biology say the experiment did teach a lot about the mysterious process of imprinting.
And Tomohiro Kono has other plans. He told Nature magazine that next he wants to make pigs.
This is SCIENCE IN THE NEWS, in VOA Special English.
Biologists have reported about a group of male baboons that are unusually nice. The biologists are Robert Sapolsky and Lisa Share of Stanford University in California.
Their work involves a group of olive baboons at the Masai Mara Reserve in Kenya. Mr. Sapolsky began the study in nineteen-seventy-eight. The baboons slept in the trees near the visitors center. So Mr. Sapolsky called them the Forest Troop.
In the early nineteen-eighties, workers dug a large hole near the building to throw trash away. Members of Forest Troop began to search through the waste for meat and other food. However, another troop of baboons had already claimed the area. They became known as the Garbage Dump Troop.
Adult male baboons are not known for their ability to share. The Garbage Dump males and the Forest Troop males often fought. So, only the most aggressive males from Forest Troop would go. These were the high-ranking baboons in the troop. Such males are at the top of the social order.
In nineteen-eighty-three, however, tuberculosis began to spread in the garbage dump area. All the high-ranking Forest Troop males got sick with the lung disease and died. Only the least socially powerful males remained.
After that, Mr. Sapolsky observed that aggressive actions within Forest Troop greatly decreased. He ended his observation in nineteen-eighty-six. He began to study another troop of baboons.
Then, in nineteen-ninety-three, Mr. Sapolsky again observed the Forest Troop. This time he went with Lisa Share. They found that the males were still much more gentle compared to other baboons. But the scientists also found something else. All the adult males in Forest Troop at that time were from other troops.
All the ones that were in Forest Troop in nineteen-eighty-six had died or moved on. Male baboons move into other troops when they become adults. The scientists wondered why the new members of Forest Troop were not aggressive like other male baboons.
They say it appears that the females are teaching cooperation to males that enter the troop. They say the females present themselves to the new males sooner than females of other troops. The female also begin to care for the males by cleaning insects from their hair sooner than normal. The males also groom the females this way.
Robert Sapolsky and Lisa Share say adult males in Forest Troop do have some things in common with other male baboons. For example, those at the top of the social order stay at that level for about a year. High-ranking Forest Troop males mistreat lower-level males, just like in other troops. However, the mistreatment is less severe.
The scientists took blood from lower-ranking members of Forest Troop. They did this to measure levels of hormones produced by tension. They say the blood tests found lower levels of these stress-related hormones than usual.
The two biologists plan to continue to watch the Forest Troop in Kenya. They note that some animals pass along culture by teaching things like tool making or communication. They say the baboons in Forest Troop pass along their unusual social rules as part of their culture. And the scientists suggest this is mainly thanks to female guidance.
The findings appear in PLoS (pronounced ploss) Biology. PLoS is the Public Library of Science. Internet users can read this scientific journal free of charge. The Web site is publiclibraryofscience.org. Again, the address is publiclibraryofscience.org.
Modern humans have a bigger brain and a smaller jaw than our ancestors. Some scientists in the United States have a theory to explain why. They say this may all have been the result of a change in one gene.
The scientists are from the University of Pennsylvania in Philadelphia. Their report is in Nature magazine. Hansell Stedman and Nancy Minugh-Purvis led the team.
The team studied a protein called myosin. Myosin is what provides power to muscles. It permits them to tighten for movement.
The scientists say they found that a change took place in a myosin gene about two-and-one-half-million years ago. This change, or mutation, prevented the gene from producing a form of myosin called M.Y.H.-sixteen. The scientists tested genetic material of people from all over the world. They found this change in all cases.
The scientists also looked at D.N.A. from seven other kinds of primates besides humans. These included the chimpanzee and macaque monkey. The scientists did not find the mutated gene in any of them. All of these animals have the gene that produces M.Y.H-sixteen. The scientists found that this kind of myosin is involved mainly in biting and chewing.
Two-point-five-million years ago was just before a period of major change in the human head. The fossil record shows that our jawbones shrank and brains grew larger beginning around two-million years ago.
Nancy Minugh-Purvis offers a possible explanation: Without the myosin, jaw-muscle size and force decreased. This removed pressure on the skull. And that freed the brain to expand. Something to keep in mind.
SCIENCE IN THE NEWS was written by Caty Weaver. Cynthia Kirk was our producer. This is Bob Doughty. And this is Sarah Long. Listen next week for more news about science, in Special English, on the Voice of America.