The origin of monogamy among mammals has perplexed scientists for some time and two separate studies tackled that very question, the Los Angeles Times reported.
One study, published Monday in Science, argued that mammals developed monogamous mating practices because females were too far apart. The other, published Monday in Proceedings of the National Academy of Sciences, suggested males adopted monogamy to protect their offspring from rival males.
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Monogamy is not common among all species and not even among mammals. According to the studies, 29 percent of species are monogamous, primates and humans among them.
One of the leading theories is the responsibility of parenting causes the male to ensure the survival and well being of his offspring. In polygamy, a male will have multiple mates and sow his seed without the same parenting responsibility.
Another prevailing theory has been that certain species realized it was easier to protect one mate instead of several. A third theory is defense against infanticide, coinciding with the first theory of protecting and ensuring offspring's well being.
Both research teams analyzed the living situations of thousands of mammals alive today and used mathematical models to work their way back through the events that led to present tense.
University of Cambridge evolutionary biologists Dieter Lukas and Tim Clutton-Brock, co-authors of the Science study, categorized the mating systems of 2,545 species of mammals. They found 61 species to have made a change to monogamy, and 60 of those species to have lived a solitary life. As females became independent, likely to gather food and provide protection for their offspring, males took notice.
They also found fatherly instincts and characteristics to have developed after becoming monogamous. This would suggest being a father is an effect of monogamy, not a cause, as many monogamous species do not require fathers to raise offspring.
PNAS study author Christopher Opie, biological anthropologist at University College in London, and his team concluded that infanticide was the only explanation that stood firm. They found monogamous species to have ancestors who committed the killing of infants and likely evolved to prevent that from happening.