How did Archer time-travel into his own body?

Question

I think it is well-understood that Star Trek has almost never handled time travel with much consistency to speak of. Any time someone travels to the past, the effects of their actions on the future are handled in any number of ways.

However, as far as I can recall, the doppelganger issue is the one thing that is typically not messed with. Either the traveler goes to a time and/or place where they don't have to worry about their doppelganger, or they do have to worry about them and either avoid or interact with them as deemed necessary by the plot.

Then we have the Enterprise episode Shockwave.

In this episode, Archer is transported 10 months into the past - back when he was on Earth, just prior to the events of the series premier. However, instead of being brought back as himself from the current time, he seems to have been transported into the body of his former self.

This is perhaps better (or worse, I'm not sure) explained in the exchange between Archer and Daniels.

ARCHER: So, you're telling me you brought me back, what, ten months ago? How about Jonathan Archer ten months ago? Where's he?
DANIELS: He's you

Is this form of time travel, thus far unique to the Star Trek universe, ever explained? It did seem slightly reminiscent of Bakula's Quantum Leap days - I was actually a little disappointed at the lack of an "Oh, boy!". But I've never seen it in Star Trek before.

Answer 1

I strongly suspect it's just due to the advanced technology that Starfleet has in the future Daniels is from.

We've seen something similar before, and the capability that Daniels has could easily be an extension of it: In VOY 5x24, Relativity, on the Federation timeship Relativity, from the 29th century.

At the end of the episode, Janeway is told that the different versions of Braxton will be "reintegrated" prior to their trial. They also reintegrate Janeway and Seven of Nine with their past selves, to preserve the timeline.

Daniels is from the 31st century. In the intervening ~200 years, they could have gained the ability to undo reintegration, preventing the younger self from retaining any memory of the event.

Almost all the other time travel events have been done with far inferior technology, or accidentally.

Answer 2

Time traveling into your own body at an earlier point in time is something that has happened before in Star Trek. It is first introduced in TOS 1x19 "Tomorrow is Yesterday" USAF Captain John Christopher and a random security guard are transported back into their own bodies. Voyager 5x24 "Relativity" the practice of transporting people into their past selves is called "reintegrating".

Answer 3

Star Trek: Enterprise always tried to show without going in details that "31st century Time Travel was very complicated for us to understand." That's why we didn't see any time machine which is common with most of sci-fi canons. And, your question is its great example.

My speculation (without canon backup):
There are multiple instances of universe defined with various possible combination of strings. Daniels could have used that to port Archer to his younger-self without switching timeline and without tampering the real young Archer.