▁life " ▁consisting ▁of ▁three ▁lines ▁of ▁descent ▁for ▁which ▁they ▁introduced ▁the ▁term ▁domain ▁as ▁the ▁highest ▁rank ▁of ▁classification . ▁They ▁also ▁suggested ▁the ▁terms ▁b acter ia , ▁arch ae a ▁and ▁e uk ary ota ▁for ▁the ▁three ▁domains . ▁ ▁The ▁model ▁of ▁a ▁tree ▁is ▁still ▁considered ▁valid ▁for ▁e uk ary otic ▁life ▁forms . ▁, ▁research ▁into ▁the ▁earliest ▁branches ▁of ▁the ▁e uk ary ote ▁tree ▁has ▁suggested ▁a ▁tree ▁with ▁either ▁four ▁or ▁two ▁super groups . ▁There ▁does ▁not ▁yet ▁appear ▁to ▁be ▁a ▁cons ensus ; ▁in ▁a ▁review ▁article , ▁Roger ▁and ▁Sim pson ▁conclude ▁that ▁" with ▁the ▁current ▁pace ▁of ▁change ▁in ▁our ▁understanding ▁of ▁the ▁e uk ary ote ▁tree ▁of ▁life , ▁we ▁should ▁proceed ▁with ▁ca ution ." ▁ ▁In ▁ 2 0 1 5 , ▁the ▁first ▁draft ▁of ▁the ▁Open ▁Tree ▁of ▁Life ▁was ▁published , ▁in ▁which ▁information ▁from ▁nearly ▁ 5 0 0 ▁previously ▁published ▁trees ▁was ▁combined ▁into ▁a ▁single ▁online ▁database , ▁free ▁to ▁brow se ▁and ▁download . ▁ ▁In ▁ 2 0 1 6 , ▁a ▁new ▁tree ▁of ▁life , ▁summar izing ▁the ▁evolution ▁of ▁all ▁known ▁life ▁forms , ▁was ▁published , ▁illustr ating ▁the ▁latest ▁gen etic ▁find ings ▁that ▁the ▁branches ▁were ▁mainly ▁composed ▁of ▁b acter ia . ▁The ▁new ▁study ▁incorpor ated ▁over ▁a ▁thousand ▁newly ▁discovered ▁b acter ia ▁and ▁arch ae a . ▁ ▁Hor izontal ▁gene ▁transfer ▁