If Adam's bridge was man-made, what is history of Adam's Bridge? would not it be a straight bridge instead of a curved one?

Adam & Eve were first humans (Manu & Satrupa, for namesake), Rama came way later, when earth was pretty much populated.

Note: Here, I'm not undertaking the biblical accounts of first humans, I'm undertaking the vedic account of first humans, or dharmic account of first humans, according to them; Manu & Satrupa were first humans, and later all the god incarnations followed throughout 3 yugas. It would also seem likely that knowledge of terrain before sea level rise helped determine the best path for the bridge.

Remember, there is a reference to praying to the sea before trying to build the bridge? This can be artistic license to talk about taking ocean currents into consideration.

had brought home a Gunny Bag full of the rock samples of the strata that makes up the Ramsethu Bridge and those rocks float in Briny Water. The Ramsethu Bridge is definitely not a natural phenomenon.

The reason a part of Bridge got submerged and curved is because of the several cyclones and tsunamis that have hit it in the last 5000 Years … the recorded super cyclone of 1967 and the Recorded Tsunami of 2004 are just two such instances to Hit Ramsethu Bridge. The Bridge has seen innumerable of such occurrences. 

Anything artificially built, several thousand years ago would start appearing natural unless some never rusting alloys are found. Maybe there is something holding the rocks in place. We will never know.

You need to understand six things.

One:

First of all it's is not Adam's Bridge. Adam is believed to be lived in a time period way older than the time period of the construction of the bridge. The Bridge is popularly referred as Rama Sethu because there are more signs that say it was built by Lord Rama.

Two:

Why do you think a man-made bridge should only be straight? Do you think the below bridge is not man made?

Three:

Now the question arises, why the above man made bridge is curved? They could have made it straight as there is no obstruction. Well, here the answer.

The bridge requires a solid foundation. However, sometimes engineers come across loose sea floor and hence make the bridge curvy.

Four:

So the Rama Sethu was made curvy for the same reason? May be or may be not. It is hard to say. However, it is also quite possible that Rama Sethu was built straight and the constant water flow for thousands of years has made it a little curved.

Five:

Now someone will comment, how can a straight bridge become a curved one? Let me remind you, Rama Sethu was not build by cement. It was build by stones and rocks. Water flow can dislocate the rocks a little.

Six:

I have gone through the map. As far as I see, Rama Sethu is the shortest distance between India and Sri Lanka. May be that's a sign of a man made bridge. People usually make the bridge between shortest distance to save time, effort and energy.

Obviously is impossible to answer.

The XVII century is, well, a century.

Probably who asked the question has a very 2D vision of time, with events far from now flattened in an unidimensional confusion (clearly, I’m jocking 😉, I mean no offense to the OP, who made a good question). Political borders are well different in 1601 and in 1699, the same way are very different in 1901 and 1999 “where the hell are the Tzarish, Austro-Ungarian and Ottoman Empire? Those India and Pakistan, are still under British rule, right? All this states in Africa are colonies?” this is what would say someone from 1901 seeing a 1999 world map. Obviously the difference would be much greater for someone from the XVII century seeing a XXI century map.

Second reason is impossible to answer is that the reaction would be very different for people leaving in seventeen century in different areas of the world.

The reaction of an Australian Aboriginal would be very different from the one of a Navajo, a Chinese or a British (or better, English) person.

A Navajo would say: “what are those United States of America? You mean all the nations and tribes unified? Are even the white man part of this coalition or we managed to drive them back to Europe?” Of course this phrase would have been possible for a 1699 Navajo. A 1601 Navajo would only know about the Spaniards in the south.

An Australian aboriginal would have said: “so this is the world? Can you point were my tribe is, please?”

A (learned) Chinese would have noticed changes in his country borders and would have some academic interest for the drastic changes in other countries.

An Englishman would say: “How odd, we lost most of Ireland but we gained Scotland!”

But, I guess, the question (as usually this questions are), meant from an Eurocentric point of view.

Well… first of all that’s how they viewed the world.

Australia is missing (they didn’t discovered it yet) and East Asia/West North America weren’t properly mapped .

So, first thing all they would have been curious about those white corners or their maps we finally mapped.

Than…

From an European point of view many reassuring parts of the maps are the same: “Well, France, Great Britain, Spain and Portugal are more or less the same.” A person from those countries would notice that first. A person from the Holy Empire or an Austro-Hungarian would first see what a British sees in a second moment. “Wait, what is Germany? Where are the Empire’s principalities? They put all in the same color cause they were too small? Where is the Ottoman Empire? Is Italy unified!?”

Than they start noticing things out of Europe, even if probably they’ll care less: “ok, what is this Australia? Why they put in different colors all the Spanish Empire Viceroyalties? Is this an administrative division? Ok, at least Brazil is still Portuguese! What are those United States and Canada? Are all the United States a Dutch colony or are they British? This Canada is French? Or are they a pagan confederation of savage tribes? Ouh, you managed to map the inner part of Africa? So those are the negro kingdoms? Those negro kingdoms are bigger than we thought, did they ever tried to invade Europe? Well, Russian Empire [Russia wasn’t usually considered European by other Europeans, back than] is more or less the same, I guess the tzars managed to repel the Mongolians from the eastern part of their Empire and are quite happy now! Well, China and Japan are more or less the same, not a surprise, since they don’t let anyone in.”