human
Considering the provided database schema and associated query, produce SQL code to retrieve the answer to the query. 
###Database Schema: common name, protein name, divergence from human lineage (MYA), accession number, sequence length (aa), sequence identity to human protein
###Question: What is the sequence length (aa) of the protein with the common name Purple Sea Urchin and a divergence from human lineage less than 742.9?
gpt
SELECT SUM sequence length (aa) FROM table WHERE common name = purple sea urchin AND divergence from human lineage (MYA) < 742.9