If you're holding out for Mr. Right, then you may be better off settling for Mr. Right Now. Evolutionary scientists claim that the human race's survival has been helped by the fact people are risk-averse when it comes to relationships. They say our nature— 1 back to the earliest humans–has evolved so that we take the safe bet when 2 are high, such as whether or not we will mate. 'Primitive humans were likely forced to bet 3 whether or not they could find a better mate,' said Chris Adami, Michigan State University professor of microbiology. They could either choose to mate with the first, 4 inferior, companion and risk inferior offspring, or they could wait for Mr. or Ms Perfect to come 5 . 　　'If they chose to wait, they risk never 6 .' Professor Adami and his team used a computational 7 to trace risk-taking behaviours through thousands of generations with digital 8 .The researchers programmed them to make decisions in a similar way that natural ones, such as humans, must make in real life. 'An individual might hold out to find the perfect mate but 9 the risk of coming up empty and leaving no progeny,' Professor Adami said. 'Settling early for the sure bet gives you an evolutionary 10 , if living in a small group.' The team tested a number 11 that influence risk-taking behaviour and found that certain conditions influence our decision-making process. The decision must be a 12 , once-in-a-lifetime event and also have a high payoff for the individual's future – such as the 13 of producing children. 　　How risk averse people is linked to the size of the group in which they are raised. If raised in a small group—fewer than 150 people—people tend to be much more risk averse than those who were part of a larger community. It turns out that 14 humans lived in smaller groups, about 150 individuals. Because resources tend to be more 15 in smaller communities, this environment helps 16 risk aversion. 'We found that it is really the group size, not the total population size, which 17 in the evolution of risk aversion,' said co-author Arend Hintze. 　　However, not everyone 18 the same level of aversion to risk. The study also found that evolution doesn't prefer one single, 19 way of dealing with risk, but instead allows for a range of less, and sometimes more-risky, behaviours to 20 . 　　'We do not all evolve to be the same,' Professor Adami added. 'Evolution creates a diversity in our acceptance of risk, so you see some people who are more likely to take bigger risks than others. We see the same phenomenon in our simulations.'