The researchers studied guinea pigs to understand how traits like litter size and body weight are inherited. They looked at data from many guinea pigs and found that genetics play a role in these traits. They also found that the number of babies born alive can affect the weight of the babies. The researchers discovered that certain traits are passed down from parents to offspring. They also found that there are relationships between different traits, like litter size and body weight at different ages. Overall, the study showed that genetics play a significant role in determining litter size and body weight in guinea pigs.