All else aside, I think there is agreement in this forum that while Blackmun relied on a great number of opinion based sources, he totally ignored the specific merit of the biology involved by lumping everything together and then saying there was no consensus.
Did that answer the pivotal question? No, it did not, and Blackmun, by his use of the words, "the judiciary, at this point in the development of man's knowledge, is not in a position to speculate as to the answer.[to the question of whether life begins at conception]", simply dumped the whole thing into the lap of a future court.
Perhaps things were insufficiently clear to Blackmun in 1973. However, during the intervening thirty-three years, scientific and technological advances have caused man's knowledge to develop to the point where there is no longer any doubt that human life begins at conception.
The next time a question hinging on whether life begins at conception comes before the court, "Roe", itself, will be aborted.
The political solution wrought by Blackmun will be displaced by the scientific solution which eluded him.