Why does the last grow the fastest?

Evelyn is cruising now.  She is everywhere.  My sister says that she is a smaller version of me. She loves the cats and is super independent.  She is almost 9 months old now and is the master at standing up on furniture and her balance is getting really good.  She came into the kitchen this morning wearing socks and stood up balancing on the cabinets and scooted down the way.  ON A SLIPPERY FLOOR! I was impressed and sad.  She is such a big girl!