Notes from the 4th class of the Big Ecology Conservation Course by Course Volunteer Bob Herbert
Big Ecology’s fourth class was presented by Joseph G. Lorenz, PhD and we explored the various levels of parenting that exists between primates and other species. Humanity is perhaps the pinnacle of evolution on our planet and as Dana pointed out in the first class, our brains consume more energy than any other species, and we learned from Dr. Lorenz that humans are also the slowest to develop. As the complexity of the human brain has increased, so too has the length of time required to raise a child and prepare them for modern civilization. It takes humans almost two decades more than any other species to get their offspring ‘out of the nest.’
Parenting behaviors evolve and adapt over time, but the common goal shared by primates and algae alike is the continuation of the species. Life finds a way, and the higher up the food chain you go (in general), the more complex the role of parenting becomes.
Parenting developed as a result of sexual reproduction. Asexual reproduction only requires a “parent” to split in half, and the two remaining parts share identical DNA. Asexual reproduction, however, does not allow for the diversification of species the way sexual reproduction does. The sharing of genetic material through sexual reproduction is the driving force behind the incredibly complex ecosystem we live in. It explains how so many different species of birds, amphibians and mammals have come to exist.
There are two types of sexual reproduction; external and internal. Fish are a good example of external fertilization. The male fish fertilizes the eggs after the female has excreted a large amount of them into the water. This process may not win him father of the year, and he may not be a scout leader, but thousands of eggs are fertilized at one time and the species perpetuates. Internal fertilization can result in the laying of an egg, which is the case with birds and reptiles. Internal fertilization can also result in the mother carrying the offspring inside her womb until she gives birth to living offspring. The higher up the evolutionary ladder we climb we discover that internal gestation is the preferred method. This allows for better protection of the young offspring for longer periods of time, as well as increased nutrition via the mother’s blood. This type of reproduction was necessary to develop higher functioning brains like the ones we find in primates and ourselves. The placenta provides a direct interface of nutrition between the mother and child, unlike an egg which relies on the finite amount of nutrients available in the yolk sack.
The more developed the species, the more parenting is needed. Feeder species like mice are able to produce multiple litters each year and their offspring are expected to be on their own within a matter of weeks. As a result, they lack the necessary survival skills needed for longevity. Survival and social skills are both taught by more evolved creatures. The fact that mice don’t remain by their parent’s side for a year and learn how to increase their chance of survival is how they fit into their niche in the food chain. When you climb the evolutionary ladder and you arrive at chimpanzees and humans there is an increased amount of energy and time that is required to properly prepare and socialize offspring.
The quantity of offspring produced by different species clearly shows this parenting phenomenon. Species engaged in asexual reproduction are capable of spawning 500,000,000 offspring per year. Fish have approximately 8,000 offspring each year, frogs have 200, rabbits have 12, cougars have 2, and primates only average one offspring every five years.
The next thing we learned was the classification between ‘r’ species and ‘K’ species. ‘R’ species are more plentiful and they pursue a life of reproduction based on “quantity.” They can survive in a wide variety of habitats, including “weedy” or disturbed areas. Mice fit into this category. “Quality” reproduction is the choice of ‘K’ species and Gorillas and humans both fit into this category. They are more specialized and don’t respond as well to environmental changes or disturbances as “r” species.” The difference between small annual plants (‘r’) and mature forests (‘K’) can also be seen in the plant kingdom. When we look back over long periods of earth’s history we see that the ‘r’ species have had the highest rate of survival, bacteria being the best example of this. Climate and environmental changes have consistently affected the ‘K’ species more dramatically, to the point of extinction in some cases. This is a direct result of the amount of parenting required and the number of offspring produced by each species.
Our brain and the brain of all primates has been developing and increasing in size and complexity for two million years. Chimpanzees are the closest living relatives to humans and in a few film clips of social research we saw that a human baby and a baby chimpanzee show glaring similarities in the way they behave. We may have lost some hair, but it was apparent that a human infant and a baby chimpanzee’s brains are organized alike. When the same challenges or stimuli were presented to each, they responded and problem solved in very similar ways.
One invention that has arisen through human evolution and is exclusive to our species is grand-parenting. Because of our longevity, humans reach an age when they are no longer able to reproduce, but we still have a lot of good years left in us. The human brain allows for the accumulation of knowledge and wisdom throughout our lifetime, which enables grandparents the opportunity to care for and teach the children of our species. This additional layer of education and care is unique to humanity. We see shared care amongst primates, however it is not as family driven as it is with humans. If a parent is killed in the animal kingdom their offspring are often adopted and cared for by other members of their species, but it is based around survival, not continued education and family lineage. Grandparents offer a fresh perspective for a child, and they bring to the table a lifetime of experience.
The development of agricultural societies drove the need for grand-parenting amongst Homo sapiens. Hunters and gathers actually spent less time seeking or making food which allowed them more time to raise their young. Farmers had to spend more time in the fields, which gave them less time to raise their children. The more complex our society becomes, the less time parents have to raise their children. As a result, grand-parenting has continued to increase its presence in American society over the past half century. More and more families have two parents in the work force, which has increased the role that many grandparents take in the lives of their grandchildren.