By Malavika Vyawahare Over the past 50 years, lion numbers have decreased by three-quarters. Only 20,000 to 40,000 of these majestic big cats survive in the wild today. A third of lion deaths are a result of poaching, and even where lions are killed in retaliation over livestock predation, in many cases their body parts are harvested for sale. Wildlife crime investigators face a big handicap when dealing with confiscated wildlife products. Sifting through dismembered remains — claws, bones, teeth — it is hard to say where they originate from. To trace lion parts to their source populations, re…