s ▁short est ▁book . ▁It ▁is ▁illustrated ▁by ▁L alla ▁Ward , ▁Daw kins ' s ▁wife . ▁The ▁book ' s ▁name ▁is ▁derived ▁from ▁Gen esis ▁ 2 : 1 0 ▁rel ating ▁to ▁the ▁Garden ▁of ▁E den . ▁The ▁King ▁James ▁Version ▁reads ▁" And ▁a ▁river ▁went ▁out ▁of ▁E den ▁to ▁water ▁the ▁garden ; ▁and ▁from ▁th ence ▁it ▁was ▁part ed , ▁and ▁became ▁into ▁four ▁heads ." ▁ ▁River ▁Out ▁of ▁E den ▁has ▁five ▁chap ters . ▁The ▁first ▁chapter ▁l ays ▁down ▁the ▁framework ▁on ▁which ▁the ▁rest ▁of ▁the ▁book ▁is ▁built , ▁that ▁life ▁is ▁like ▁a ▁river ▁of ▁gen es ▁flow ing ▁through ▁ge ological ▁time ▁where ▁organ isms ▁are ▁mere ▁temporary ▁bodies . ▁The ▁second ▁chapter ▁shows ▁how ▁human ▁ancest ry ▁can ▁be ▁trac ed ▁via ▁many ▁gene ▁path ways ▁to ▁different ▁most ▁recent ▁common ▁ancest ors , ▁with ▁special ▁emphas is ▁on ▁the ▁African ▁E ve . ▁The ▁third ▁chapter ▁describes ▁how ▁grad ual ▁enh ancement ▁via ▁natural ▁selection ▁is ▁the ▁only ▁mechanism ▁which ▁can ▁create ▁the ▁observed ▁complexity ▁of ▁nature . ▁The ▁fourth ▁chapter ▁describes ▁the ▁ind ifference ▁of ▁gen es ▁towards ▁organ isms ▁they ▁build ▁and ▁disc ard , ▁as ▁they ▁maxim ise ▁their ▁own ▁utility ▁functions . ▁The ▁last ▁chapter ▁summar ises ▁mil est ones ▁during ▁the ▁evolution ▁of ▁life ▁on ▁Earth ▁and ▁spec ul ates ▁on ▁how ▁similar ▁processes ▁may ▁work ▁in ▁al ien ▁planet ary ▁systems . ▁ ▁The ▁digital ▁river