Bill Gates demonstrated with a short, less-than-two-minute video Thursday just how much he's evolved over the years.

The occasion was -- well, it's an unusual occasion: 10 years since he first joined Twitter. He marked it by sharing his seven favorite tweets, among the 3,249 that he's tweeted since 2010. 

Here are the ones he picked. As a window in time, it's interesting to see which small handful out of his 3,249 tweets made the cut. And when you look at them together, I think they all have one key thing in common. 

1.    The most mind-blowing fact

Strong opener, and it cites Gates's friend and favorite author, Vaclav Smil. In December 2014, Gates tweeted about "the most mind-blowing fact I learned this year," namely that between 2011 and 2014, China used more cement than the United States used in the entire 20th Century.

2.    The ice bucket challenge

Like everyone else on social media in summer 2014, Gates poured a bucket of ice cold water over his head to raise money and awareness for ALS. Interesting that he challenged Elon Musk, Ryan Seacrest, and Chris Anderson of TED.

3.    Vaccines

"I often say vaccines are one of the best health investments," Gates tweeted in December 2014 (yes, close in time to the cement tweet), including his prediction that by 2015, Gavi, The Vaccine Alliance would have contributed to preventing 3.9 million deaths.

4.    Toilets

November 2018: "There are few things I love talking about more than toilets."

Among his points: the poorest 2.5 billion people in the world don't have steady access to toilets, and unprocessed human waste is a major health hazard. 

5.    I hate mosquitoes

From August 2018: "[M]osquitoes kill more people in one day than sharks kill in 100 years."

6.    Promoting Melinda's book

If my wife wrote a book and I didn't mention it among my seven favorite tweets, I'd probably be in trouble. Plus, he got President Obama to do a cameo. Actually, more than a cameo.

7.    The most beautiful chart

Child deaths cut from 12.1 million a year in 1990 to 5.8 million in 2015. This tweet links to a very long and fascinating update on progress in some of Gates's favorite causes, written in the form of a letter to Warren Buffett. 

Gates on caring

I wrote not long ago about how Gates cited his wife, Melinda Gates, and Buffett, with being the two people who have most influenced his thinking

At the time, he cited a quote from Buffett, as being the barometer of true success: "Do the people you care about love you back?" 

I don't think you can look at the seven tweets Gates picked out of his 3,000-plus, and not realize that they are all about either one of two things: the people he cares about, or the causes he's decided to dedicate the second half of his life to, since he stepped down as chairman and CEO of Microsoft.

Here's the commemorative video Gates posted. (Add "dad humor" to his list of strenghts.)