Most people can't? Seems easy to me. Those plus movements like I was playing a trumpet put a smile on the face of my orthopaedic surgeon after he put my right elbow back together. It was put into piece from a large bike racing crash. Didn't race after that. My day job seemed more important.

Can you do bird calls? Maybe a Bonelli's Warbler? (it's a very obtuse movie reference)

"I used to whistle everywhere - jazz standards and classical numbers mostly, biking or walking or taking a shower."

I don't whistle, but for a long time, I've been vaguely aware that I hum everywhere-- classic rock standards and indie rock numbers mostly--while biking or walking or driving.  The Feeshko has frequently pointed that out to me, but it REALLY became obvious when I started noticing that I'm usually humming at the beginning of the short videos I make for my Cycleblaze journals.  I didn't even know I was doing that until I heard it myself.  I'm glad to hear you are recovering your whistling skills, and I thank you for sharing that little tidbit.  It helps us to get to know you a little bit better.

I know, it seemed easy to me too.  When I first read that most people can't do it, I challenged a bunch of friends.  Sure enough, less than 50% could do it effortlessly.  Therefore, based on my own scientific research, it is true.

I was never a bike racer, but after reading about a surgeon having to put your elbow back together, I decided I will never become one in the future.  Nevertheless, I thank you for participating in this forum and helping us get to know you a little better.

As an introvert, it's very difficult and uncomfortable for me to share anything about my life. However, because it's Greg who asked, I'm going to put some information out there, after which the people who read this will know more about me than all of my coworkers, and most of my extended family. I'm also doing it to prime the pump, because so few have responded, but mainly because it's Greg asking.
Random facts about me:
* I grew up on the industrial side of Houston, along the Ship Channel.
* I played tennis in high school.
* I received a Bachelor's degree in Psychology from Baylor, then a Master's of Divinity degree in California. The latter will surprise many of the people who know me, because I'm a completely different person now.  
* I worked as a librarian at the Main Library in downtown Houston. Working there was really interesting because it was prior to Google, and people would call Telephone Reference to ask those weird questions that everyone now looks up online. A few examples include: "Is there a perfume made out of whale vomit?" "How many votes does a Siamese twin get?" and “Someone wrote an autobiography of Katherine Hepburn entitled Me. Can you tell me who the author is?”  (yes, two, and Katherine Hepburn - I have dozens)  FYI, working at a library isn't just a matter of sitting around reading (although one of my favorite things is sitting around reading), and when you work in the downtown area of a large metropolitan city it can get more exciting than you'd expect (example: large homeless man sweeps everything off counter, picks up computer and shatters hurricane-proof glass window with it, but not before completely stripping off all of his clothing)
* In my mid-30s I went back to school to become a Physician Assistant. It's a relatively new profession, started in 1965 by medics from the VietNam war out of the need for medical providers in rural areas. I don't know if there's an equivalent in other countries. Another name is "Advanced Practice Provider," and recent laws have passed which allow us to practice independently and without supervision, just like a physician (although I've always practiced pretty much independently because I was rural). I'm able to prescribe medications, suture people up, run a code (administer drugs and use the paddles when a person goes into a fatal arrhythmia), do biopsies, etc. Becoming a PA is the second best decision I ever  made.
* I practiced in two small towns in Texas (Munday, with 900 people, and Knox City, with 1200) which, coincidentally, I passed through on my 1982 trip. The entire county had ~4,000 people. After that I practiced at the Mayo Clinic in Minnesota, then moved to Iowa City and started working at the VA seeing veterans.
* Consequently, I now have two Bachelor's degrees, and two Master's degrees. Even so, I'm not really that smart. I'm not simply being humble; I've always had to study twice as much as everyone else. But, since I'm naturally curious and like to learn new things, I've never minded the extra effort.
* Also related to my work: having practiced in Texas, I can have a conversation with you in Spanish, but only if you have a medical problem.
* I really loved my job, but retired on 9 January. I'd still be doing it, but I'm 66 years old, and there are some things I'd really like to do while I'm still healthy enough to do them. You'll eventually be able to read about them on CycleBlaze if you're so inclined.
* After grad school in the San Francisco area, I became a Level 1 ASL interpreter. An interesting side note about sign language is that American Sign Language is actually much closer to French Sign Language than it is to British Sign Language because of their origins. It's been a long time since I signed.
* While in the San Francisco area, a friend and I decided to see what it was like to be homeless, so we had our wives drop us off in the middle of Golden Gate Park. After arriving at the shelters too late to get a bed we ended up trying to find a warm place to sleep... anywhere, really, but ended up freezing our butts off attempting to fall asleep in some bushes. I wouldn't do well as a homeless person.
* Also while in the San Francisco area, I volunteered at the San Quentin State Penitentiary, and have some stories to share if we ever have the opportunity to sit down to a meal and a drink together. I hope we do.
* There have been times as a parent when I had less than five dollars in the bank and no food whatsoever, but things always worked out.
* When my first wife of six years left me I continued raising my stepsons, finally adopting them when they were in their forties. I'm extremely proud of both of them.
* I have a Private Pilot's license.
* I took my first drink of alcohol at the age of 46. Having been raised in a very conservative home, there wasn't any around, and it was just one of those things I never thought about as an adult. I now have a well-curated wine collection, but no longer drink much now that the more recent data shows it's more harmful than beneficial.
* I'm the luckiest person you've ever known.
* I'll leave this up for a couple of weeks, then most likely delete it. I'm really squirming.
* I’d love to hear about you.

Thanks for helping us get to know you a little better, Mark.  I learned you were a very interesting guy when we met last year, but now I know you are even more of an interesting guy than the interesting guy I thought you were.

What Greg said, I'm glad you have put yourself out there on this forum and confirms my belief that everybody has a story. Yours is a really interesting one, and I mentally put you in my made-up category of "serial obsessionist". You may be an introvert but you're an introvert who loves and cares about people. Folks don't often get that nuance. Anyway, welcome to retirement, you're going to love it, I promise.

A lot of what you can learn about me is on my profile. But of course, there is more. I was married and had kids in my early 20s, and skipped a lot of your typical wild oats sowing and so forth. After my second marriage failed, I quit my job, sold my house, took the youngest child to college, moved to Portland, and took a year off from working to get my head together and live independently for the first time in my life. I didn't sow any wild oats then either, I took up with Bruce, who has been my friend since 1978. We've been together almost 23 years now. 

But I did start to travel and live my life differently than I had before. I was a school library assistant, a low-paying but super rewarding job that gave me plenty of independence, creativity, and opportunities for learning new skills. Since money has never been that important to me, like Mark Bingham said, "I'm the luckiest person you know." I have survived one terrible car crash, one nearly fatal appendicitis, and was blinded for a week when I was 8. I can see pretty good now. I have a progressive incurable lung disease related to the asbestos in my hometown of Libby, Montana. You can read about that if you want to know further. So far, so good, mine hasn't progressed much, if at all. Thank you, bicycle.

I am a gardener, first and foremost. I read and write. I was an art major in college but never graduated. I love birds and wildlife and watching the sky. I'm a good neighbor to my neighbors, a good Oma to my grandchildren, a close and warm mama to my wonderful kids, and a loving partner to Bruce. My sisters and I have a Wordle chat group and we check in with each other every morning. My mom is 94 and golfed every day last summer. I wish I lived closer to her.

I grew up in a house with ten people in it. I've lived in a place with no running water or inside bathroom. I've owned a six-bedroom house. I've lived in a tiny apartment where the bed pulled out of the wall. Home and hearth are important to me, my living spaces have all been humble but beautiful.

I read a lot of politics, but am NOT a politician. I have a special interest in SE Asian politics, particularly in Myanmar/Burma. 

My house is painted orange and is named Casa de Mango, it has hosted several CycleBlazers and it's a wonderful little home. And every night I count my blessings, whether I sleep well or not. 

What an intriguing  summary of your life so far! Thank you for sharing.