Colin Newton, 34, a handyman for the North Uist estate and freelance pest control officer, made the grim discovery while laying traps for rats and ferrets in Griminish, on the north-west coast of the island.
He said that while laying a trap he spotted a small lower jawbone complete with teeth jutting out from the sand. He said: "I knew there were some ancient settlements in the area, but you don't expect to find a set of lower teeth.
"I plucked up the courage and had a wee scrape round about and, sure enough, the bottom jaw fell out. When I looked round about, there were other bones and I could see the spine. I knew right away it was a child's jawbone, it was so small.
"The teeth were perfect and unbelievably white. I also found a much bigger thigh bone, about the same size as mine, so I knew it had to be from an adult. The whole experience was eerie."