I started my career as a foreign correspondent in Beirut in 1979. I didn’t know it at the time, but 1979 turned out to be one of the great vintage years for foreign news — particularly from the Middle East. It set in motion the most important dynamics still shaping that region today. In fact, it’s been 1979 for 36 years. And the big question about the Iran nuclear deal reached this month is, Will it ultimately be a break from the history set in motion in 1979, and put the region on a new path, or will it turbocharge 1979 in ways that could shake the whole world?

What happened in 1979? For starters, there was the takeover of the Grand Mosque in Mecca by Islamist extremists who challenged the religious credentials of the Saudi ruling family, accusing them of impiety. The al-Sauds responded by forging a new bargain with their religious conservatives: Let us stay in power and we’ll give you a freer hand in setting social norms, relations between the sexes and religious education inside Saudi Arabia — and vast resources to spread the puritanical, anti-women, anti-Shiite, anti-pluralistic Sunni Wahhabi fundamentalism to mosques and schools around the world.

This Saudi lurch backward coincided with Iran’s Islamic Revolution in 1979, which brought Ayatollah Ruhollah Khomeini to power. That revolution set up a global competition between Shiite Iran and Sunni Saudi Arabia for leadership of the Muslim world, and it also led to a big surge in oil prices that gave both regimes more money than ever to export Shiite and Sunni fundamentalism. That is why the Egyptian scholar Mamoun Fandy liked to say, “Islam lost its brakes in 1979.”

That competition was further fueled by the Soviet invasion of Afghanistan in 1979 — which spawned the Sunni jihadist movement and eventually Al Qaeda — and by the Three Mile Island nuclear accident, also in 1979, which basically ended all new building of nuclear power plants in America, making us more dependent on fossil fuels. Of course, the Islamic Revolution in Iran also led to a break in relations with the U.S. — and shifted Iran from a tacit ally of Israel’s to a country wishing “death to Israel.”

So the U.S.-Iran nuclear deal marks a big change — but because it will lead to an end to economic sanctions on Iran, it could turbocharge 1979 as easily as end it. That depends on a lot of factors: Will the nuclear deal empower the more moderate/pragmatic majority inside Iran rather than the hard-line Revolutionary Guards Corps? The reason to be worried is that the moderates don’t control Iran’s nuclear program or its military/intelligence complex; the hard-line minority does. The reason to be hopeful is the majority’s aspiration to reintegrate with the world forced the hard-liners to grudgingly accept this deal.

A lot will depend also on Saudi Arabia moderating the anti-modernist trend it imposed on Sunni Islam. On Tuesday the Middle East Media Research Institute released a translation of a TV interview by the Saudi author Turki al-Hamad about the extremist discourse prevalent in Saudi Arabia. “Who serves as fuel for ISIS?” he asked. “Our own youth. What drives our youth to join ISIS? The prevailing culture, the culture that is planted in people’s minds. It is our youth who carry out bombings. … You can see (in ISIS videos) the volunteers in Syria ripping up their Saudi passports.”

That’s why another factor determining if 2015 is a break with 1979 or a multiplier of it will be the energy revolution in America — efficiency, renewables and fracking — and whether it keeps putting downward pressure on oil prices. Give me five years of $25-a-barrel oil and you’ll see reformers strengthened in Iran and Saudi Arabia; they’ll both have to tap their people instead of oil.

But while that oil price decline is necessary, it is not sufficient. Both regimes also have to stop looking for dignity and legitimacy in combating the other — and Israel — and find it, instead, in elevating their own people. Saudi Arabia’s attempt to bomb Iranian influence out of Yemen is sheer madness; the Saudis are bombing rubble into rubble. Will Iran spend its windfall from this nuclear deal trying to dominate the Arab world? Maybe. But Iraq, Syria, Libya and Yemen today are like a giant Superfund toxic cleanup site. Iran wants to own that? It will sap more of its strength than strengthen it. We know.

On July 9, Agence France-Presse reported that the International Monetary Fund estimated Saudi Arabia, whose population tripled since 1975, would run a budget deficit this year exceeding “$130 billion, the largest in the kingdom’s history,” and “to finance spending Riyadh has already withdrawn $52.3 billion from its fiscal reserves in the first five months of the year.” Iran’s population has doubled since 1979, and 60 percent of its residents are under 30 and it has 20 percent unemployment. Last April, Issa Kalantari, a former Iranian agriculture minister, warned that because of dwindling water resources, and over-exploitation, if Iran doesn’t radically change its water usage “50 million people — 70 percent of Iranians — will have no choice but to leave the country,” Al-Monitor reported.

Nukes are hardly the only threats for this region. Both Iran and Saudi Arabia desperately need to make 2015 the end of the 1979 era. It would be fanciful to predict that they will — and utterly realistic to predict the destruction that will visit both if they don’t.