Self Recognition, Mirror Test (Chimps and other Great Apes are not particularly spiritual)

Material culture (evident in animals other than human beings, such as the aforementioned Great Apes, who do not display what we might consider religion)

Possible avenue of exploration: burial of the dead (evident in elephants, neanderthals, and other later hominins in the lineage eventually leading to Homo sapiens).

If we assume that the common ancestor of Homo sapiens and Homo neanderthalensis had something we might recognize as religion (and technically there is no reason to assume this), than we establish a lower limit of 800,000 years ago (around the beginning of the speciation event between the lines leading to sapiens and neanderthals). This also assumes no interbreeding between phenotypically and/or culturally distinct populations which are arguably different species or subspecies (taking into account the arbitrary nature of taxonomy and thus cladistics). That’s a lot to assume, after all, neanderthals and sapiens could have developed religious tendencies without having a common ancestor. Language for all we know could have evolved twice. Reversals in evolution are rare, but parallel and convergent evolution are not. Also, there was probably gene flow between certain populations of extinct and ancestral hominids such and sapiens and neanderthals.