Natural rubber is too soft and chemically reactive for practical applications. vulcanization of natural rubber entails

Three alkali metals in group 1 are calcium, strontium, bariumboron, aluminum, galliumsodium, potassium, rubidiumfluorine, iodine, chlorine

Many archeologists and anthropologists disagree with dr. thorne's view.  thorne strongly believes that what many calls "homo erectus"  was in fact  homo sapiens,  and that they migrated out of africa almost 2 million years ago and dispersed throughout europe and asia. that's way different  from what scientists have always believed about the evolution of the species.