▁species , ▁the ▁Pro gen itors , ▁and ▁human ity . ▁While ▁most ▁humans ▁take ▁pride ▁at ▁ach ieving ▁space ▁travel ▁without ▁a ▁patron , ▁some ▁humans ▁( called ▁Dan iken ites , ▁after ▁Er ich ▁von ▁D än iken ) ▁and ▁most ▁Gal act ics ▁believe ▁otherwise . ▁ ▁S . ▁M . ▁St ir ling ' s ▁nov els ▁The ▁Sky ▁People ▁and ▁In ▁the ▁Cour ts ▁of ▁the ▁C rim son ▁Kings ▁state ▁that ▁an ▁ancient ▁race ▁of ▁al iens ▁populated ▁Earth , ▁Mars , ▁and ▁Ven us ▁with ▁human ▁and ▁animal ▁life . ▁Additionally , ▁the ▁ancient ▁astr onaut ▁theme ▁is ▁played ▁in ▁reverse , ▁with ▁the ▁techn olog ically ▁advanced ▁humans ▁from ▁Earth ▁being ▁seen ▁as ▁advanced ▁gods ▁by ▁the ▁bronze ▁age - level ▁al ien ▁n atives ▁of ▁Ven us ▁and ▁Mars . ▁ ▁In ▁William ▁H . ▁Keith , ▁Jr .' s ▁" Her itage ▁Tr il ogy ," ▁a ▁war ▁between ▁the ▁United ▁States ▁and ▁a ▁United ▁Europe ▁( and ▁later ▁between ▁the ▁United ▁States ▁and ▁China ) ▁has ▁its ▁roots ▁in ▁the ▁discovery ▁that ▁ancient ▁astr ona un ts ▁visited ▁Earth ▁on ▁several ▁occasions . ▁ ▁An cient ▁technology ▁found ▁on ▁Mars , ▁the ▁Moon , ▁and ▁Europa ▁change ▁the ▁balance ▁of ▁power ▁on ▁Earth . ▁ ▁In ▁Walter ▁Ernst ing ' s ▁The ▁Day ▁the ▁God s ▁D ied , ▁an ▁extr ater rest rial ▁civil ization ▁is ▁said ▁to ▁have ▁built ▁the ▁ru ins ▁of ▁ancient ▁Peru . ▁ ▁In ▁the ▁Out