Simplify the following text for a Grade 13 native English-speaking person.
Original: Based on this and co-occurring fossils , one plausible hypothesis for the origin of polyplacophora has that they formed when an aberrant monoplacophoran was born with multiple centres of calcification , rather than the usual one .
Simplified: The polyplacophorans may have formed when an aberrant monoplacophoran was born with multiple centres of calcification , rather than the usual one .