Viewed in its historical context it is clear how this presumption arose. From the perspective of feudal lords, a joint tenancy was preferable because the right of survivorship made it more likely that the land would vest in one tenant from whom feudal dues could be more conveniently exacted. From the point of view of feudal tenants, a joint tenancy was preferable because certain feudal services which would otherwise be due separately from each tenant in common could be avoided. For example, feudal incidents of tenure connected with inheritance could be avoided through the operation of the right of survivorship. Finally, from the perspective of purchasers of real property a joint tenancy was preferable because it made the investigation of title much easier.
Joint tenants hold a single title whereas each tenant in common has a separate title.
If a joint tenant died there remained only one title whereas if a tenant in common died, his or her share might be left to a number of persons thereby proliferating the number of titles to be searched before the land could be sold as a whole. The slightest indication that a tenancy in common was intended was seized upon. Thus, even though the legal estate might have passed by survivorship, if there were circumstances indicating a distinct severalty of interests, the survivor was regarded in equity as holding the legal estate in trust for himself or herself and the legal personal representative of the deceased co-owner. The clause as drawn raises a presumption the other way and presumes a tenancy in common unless otherwise indicated. I must say it seems to me that it is so - the present rule generally defeats the intention of the donor.