▁can ▁be ▁seen ▁as ▁forming ▁separate ▁languages . ▁Among ▁them , ▁Pro to - BC D ▁will ▁be ▁the ▁language ▁ancest ral ▁to ▁the ▁subgroup ▁B CD , ▁Pro to - C DE ▁the ▁language ▁ancest ral ▁to ▁C DE ▁and ▁so ▁on . ▁As ▁for ▁the ▁language ▁desc ended ▁from ▁dialect ▁D , ▁it ▁will ▁belong ▁simultaneously ▁to ▁three ▁" inter sect ing ▁sub groups " ▁( BC D , ▁C DE ▁and ▁DE F ). ▁ ▁In ▁both ▁the ▁tree ▁and ▁the ▁link age ▁approaches , ▁gene alog ical ▁sub groups ▁are ▁strictly ▁defined ▁by ▁their ▁shared ▁inheritance ▁from ▁a ▁common ▁ancest or . ▁Sim ply , ▁although ▁trees ▁ent ail ▁that ▁all ▁proto - l anguages ▁must ▁be ▁dis cret ely ▁separated , ▁the ▁link age ▁model ▁avoid s ▁that ▁assumption . ▁François ▁also ▁claims ▁that ▁a ▁tree ▁can ▁be ▁considered ▁a ▁special ▁case ▁of ▁a ▁link age ▁in ▁which ▁all ▁sub groups ▁happen ▁to ▁be ▁nested ▁and ▁tempor ally ▁ordered ▁from ▁broad est ▁to ▁narrow est . ▁ ▁In ▁order ▁to ▁un ra vel ▁the ▁gene alog ical ▁structure ▁of ▁link ages , ▁Kal yan ▁and ▁François ▁have ▁designed ▁a ▁dedicated ▁quant itative ▁method , ▁named ▁Historical ▁gl ott ometry . ▁ ▁Ex amples ▁An ▁example ▁of ▁a ▁link age ▁is ▁the ▁one ▁formed ▁by ▁the ▁Central ▁Mal ay o - Pol yn esian ▁languages ▁of ▁the ▁Band a ▁Sea ▁( a ▁sea ▁in ▁the ▁South ▁Mol u cc as ▁in ▁Indones ia ). ▁The ▁Central – E astern