While the origins of the Mass clearly go back to the Last Supper of Christ, the development of the liturgy does not become clear until the time of the Gelasian Sacramentary. Once ascribed to Pope Gelasius I (492-496 AD), it is assembled between the sixth and the eighth centuries. It is the oldest known Roman Missal. It presents the Roman Canon or First Eucharistic Prayer as we still know it. The trajectory of a rite clearly orchestrated by the papacy clearly begins with St. Gregory the Great (590-604). He makes three additions to the sacramentary: the use of Kyrie eleison, an addition to the Hanc igitur, and the insertion of the Our Father prior to Holy Communion. The liturgy has only known two major reforms in its long history, that of Pope Pius V (1566-1572) and Pope Paul VI (1963-1978). The Roman Rite of the Mass, both old and reformed, is in many ways quite different from the liturgies of the Eastern churches.
For instance, (1) while the current Mass of Pope Paul VI has restored the Prayer of the Faithful or bidding prayers after the Credo and homily; the liturgical litanies so often sung by clergy or that are imbedded in the canon are absent. Indeed, today, these prayers of petition are written anew for every liturgy, and while introduced and closed by the priest, are most often read by a lay person instead of by a deacon at Mass.
(2) Another point of distinction is the placement of the sign of peace after the Lord’s Prayer and prior to the distribution of Holy Communion. Most other rites place the sign or kiss of peace at the beginning of the Mass.
(3) Also, as a point of departure, our oldest continually used Eucharistic prayer (number 1) or the Roman Canon only has an implied invocation instead of a clear epiclesis to the Holy Spirit. This is remedied in the newer anaphoras (2 through 4).
(4) It should also be noted that the revised Eucharistic prayers place the various intercessions in closer proximity and in what seems a more logical progression than the Roman Canon.
While the liturgy knows some pruning prior to Vatican II, it usually experiences additions instead. Historically, the Roman Rite becomes a magnet attracting the elements of many of regional liturgies, sometimes without regard for redundancy or placement.