From the Seattle Times:
Oops, the scientist dropped his clothespin. Not to worry; a wobbly toddler raced to help, eagerly handing it back.
The simple experiment shows the capacity for altruism emerges as early as 18 months of age, the scientist says.
Toddlers' desire to help out signals fairly sophisticated brain development and is a trait of interest to anthropologists trying to tease out the evolutionary roots of altruism and cooperation.
Parents will read this and think "Yup, I've seen this." They will also remember their children shouting "MINE! MINE!" and fighting for the possession of a toy.
Having observed two Powerkids, young boys now 4 and 5, grow up, I also know that the desire for the possession and protection of private property also shows up at an early age. My unscientific but experience-based guess is that kids have some appreciation for private property rights by the age of 5 months. I watched a video of my youngest Powerkid, aged 5 months at that time, last night. He was chewing on a towel and when the Powerwife took it away, our youngest immediately began fussing and, as well as he could, grasping for the towel.