Which process can produce new inheritable characteristics within a multicelular species

Mutations

Explanation:

Random modifications within the genome may arise during the cycle of cell division, called mutations. These are errors which occur as copies of the DNA are produced within the cell; mutations may range from small modifications called single nucleotide polymorphisms to large-scale deletions and multi-gene additions.  These are transmissible across several generations, and are said to be heritable.

These mutations create variants which, within a community, become permanent, resulting in the creation of different, genetically distinct populations called species.  Mutations can even accumulate over time in a group, changing the distribution of alleles or various gene forms-this is called genetic drift.