Genes are located on long chains of DNA called chromosomes. Fertilization showing combination of chromosomes from sperm and egg Humans have 23 pairs of chromosomes: one member of each pair was inherited from the mother and the other from the father. Correspondingly, we have two versions of every gene, one from the mother and one from the father.
If people reproduced by taking 23 pairs of chromosomes from the mother and 23 pairs of chromosomes from the father, the baby would have too many chromosomes (46 pairs). So eggs and sperm carry only half the usual number of chromosomes—just 23 unpaired chromosomes, carrying one version of each gene. When the egg and sperm get together, the baby receives the normal 23 matched pairs.
When eggs and sperm are produced, the parent cell first copies each chromosome, leaving the duplicate pairs attached to one another.
Producing eggs and sperm is our first opportunity for mixing and matching genes. When the mother makes an egg, her chromosomes first find their matched partners and exchange some DNA with each other. That's called recombination. Because of this shuffling, genes from the mother’s mom and genes from the mother’s father can wind up next to one another on the same stretch of DNA. (The same thing happens in the father’s sperm.)
diagram showing chromosome recombination
Only after chromosomes recombine do they segregate into different egg cells, so that each egg cell ends up with one version of each chromosome.
When egg and sperm meet, the baby inherits a combination of genes that is totally unique: it carries versions of genes from all 4 grandparents plus any mutations that occurred when the mother and father were making the egg and sperm.
Parents can pass down epigenetic markers for many generations or their effect can be short-lived, lasting only to the next generation. Either way, the changes are temporary because they do not alter the sequence of DNA, just the way DNA is expressed.
Scientists are still trying to understand the details. The epigenetic markers that were modified by the food supplements appear to have “silenced” genes that encourage appetite. The parents’ environment—in this case, the food they ate before becoming parents—affected the weight of their offspring.
Certain types of medicine have also been suspected of causing changes in epigenetic markers, leading to cancer in the offspring of women who took the medicine. For example, a type of synthetic estrogen prescribed to prevent miscarriages has been linked to an increased number of cancers in their daughters’ and granddaughters’ reproductive organs.
The centerpiece of a treasure trove of new fossils, the skeleton—assigned to a species called Ardipithecus ramidus—belonged to a small-brained, 110-pound (50-kilogram) female nicknamed "Ardi." This new discovery throws evolution into a spin.
Ardi instead shows an unexpected mix of advanced characteristics and of primitive traits seen in much older apes that were unlike chimps or gorillas (interactive: Ardi's key features).
When one senses that one’s own way of thinking is being overshadowed, one experiences discomfort and anger, which is found in the limbic part of the brain. The central cortex of the brain seems to be confused.
Evolution of our imaginative thinking should never be locked up or isolated in any way, for isolation narrows down the scope of inspiration. As we are gain knowledge our cognizance skills also increase and that in turn brings more discoveries.