Many amateurs have contributed observations and data that have been incorporated into papers and books. Some are accepted as colleagues by their professional counterparts. They present their findings at conferences and publish papers in peer-reviewed journals. For each of these, hundreds more devote their spare time to making observations, measurements, sketches, photographs, and reports without receiving direct recognition. Although some are retired, others are taxi drivers, photographers, civil servants, pilots, or missionaries, the latter group having an especially impressive record of achievement.

What exactly is the latter group here?
So 'the latter' can be used 'the very last.' I see. 
Thanks, MM!