By Carlo Versano

The theme of Bill and Melinda Gates' annual letter for 2019 is "surprise."

The letter, dedicated to Microsoft's late co-founder Paul Allen, outlines the worldwide developments that the philanthropist power couple found the most shocking in 2018. But it also acts as a roadmap for how the Gates Foundation plans to invest in technology that will help make the world a better place in the years to come. And, as Melinda Gates told Cheddar's Kristen Scholer in an interview Tuesday, it starts with poop.

It was eight years ago that the Gates Foundation put out a challenge to the world: reinvent the toilet. Engineers took the call, and now, Gates said she can announce that the next generation toilet will be able to be produced at scale in about seven years.

Modern toilets are a wonder of the modern world ー for those who have access to them. For the 2 billion people on this planet who have to think about where they're going to go to the bathroom next, the technology hasn't improved much since the flush toilet was invented in 1775.

Toilets are especially important for women and girls in the developing world, as Gates explained, who often suffer kidney damage from holding in urine because there's nowhere safe to urinate, or skip school because the bathrooms aren't private enough for changing tampons in countries where there is still a deep stigma attached to menstruation.

The toilets being developed with Gates Foundation investments are, essentially, portable treatment plants. They can recycle solid waste as fertilizer and liquid waste as drinkable water.

"There's great ingredients there," Gates said.

Gates also told Cheddar that women in the developing world are being left out by the big data revolution.

"Data is sexist," she said. We think of it as objective, but not enough data is being collected about women's lives, especially in the developing world, which leads to incomplete data sets that drive decision making in the developed world. "What gets measured is what gets done," Gates said, and governments and philanthropists need full sets of data to be able to invest money and resources that will be impactful.

The recent advancements in commercialized DNA testing have the potential to increase the data around issues like preterm birth, which affects 10 percent of women globally and is on the rise in the U.S. (African-American women are 50 times more likely to give birth prematurely). Until recently, there was no correlation between genetics and the risk of premature birth, but by analyzing the data voluntarily submitted by users of 23andMe, scientists ー funded by the Gates Foundation ー have discovered a potential link between preterm labor and six specific genes.

"We're going to learn a lot from our genetic testing over time," Gates said, especially if genetic testing becomes an insured cost and people are confident that their privacy is being protect. Gates said "Bill and I are actually very in favor of it" and that her family has had their DNA tested via 23andMe.

Gates made what she calls a "nationalist case for globalism," noting that the U.S. spends less than 1 percent of its budget on foreign aid, even though that kind of investment promotes strength and security across the world in ways that end up benefiting both the global economy and stability in the U.S.

In the letter, the Gates' also mentioned the disproportionate power of the mobile phone in the hands of women in the developing world. Studies show women are more likely than men to reinvest their earnings in their children, but in many poor nations banking and saving is still solely the man's responsibility. Advancements in mobile banking technology can mean that a cell phone, in the hands of a mother who has the freedom to open her own account and start saving, can be one of the most beneficial technological advancements in terms of fighting childhood poverty.

That means, though, getting phones to the women who need them ー and then teaching them how to become "digitally literate," Gates said.

For the rest of us, our phones have become albatrosses ー another issue Gates said needs to be addressed. By virtually any metric, the world today is better than it has ever been at any point in human history. Infant mortality is declining, global poverty has been cut in half ー and yet we, in the developed world, feel more adrift and apart than ever.

But Gates is an optimist. "We are lucky to grow up in this country," she said.

Think about that next time you use the toilet.

Melinda Gates' new book on what she's learned about female empowerment, Moment of Lift, is out April 23.