junegoesaround5689 t1_jde2f78 wrote

Hmmmm, never heard of or tried this before.

Didn’t work for me.

If I put my thumb up in front of the object and try to focus both eyes on the object, I see two thumbs, if I focus on my thumb there are two objects about equidistant on each side of my thumb. My thumb moves when I close either eye, although slightly less with the right eye.

I am partially ambidextrose - slight right hand dominance but use both hands for similar tasks and can easily "train" the left hand to be about as effective as the right on anything, like writing, where I’ve developed a more pronounced right-handed preference.

Maybe it’s because I’m moderately near sighted? 😋


junegoesaround5689 t1_j5rypyu wrote

Evolution doesn’t (and can’t) "retrace its steps". So, almost certainly this would be impossible. It would be like two different rainstorms producing exactly the same raindrops falling in exactly the same places with identical lightening and thunderclaps. Waaaay too many variables for the exact thing to happen twice. Similar (ref convergent evolution), yeah, but not identical.


junegoesaround5689 t1_iwt1e65 wrote

The upright stance developed more than a million years before adaptations for long distance running. The running adaptations happened around the homo erectus timeframe ca 2 million years ago. The bipedal/upright adaptations occurred in the ardipithecus to australopithecus timeframe ca 4.5 to 3 million years ago with some going back even further.


junegoesaround5689 t1_iwdejpz wrote

Sperm and eggs carry half of each parent’s genome, not all of it. The process whereby sperm and eggs are formed is called meiosis.

Here are a few links to various levels of explanation:





eta: (thought I’d try to explain this a bit more to clarify how and why each child has a unique genome, except for identical twins.)

Each sperm and egg end up with half of a unique genome because of crossover during Prophase I of meiosis.

Your genome is made up of one DNA strand from your Mom and the other strand from your Dad. So exactly 50% from each parent.

During Interphase your cell duplicates your Mom‘s and Dad’s strands, still wound together but still separated as one strand from each parent in the DNA double helix. These are called sister chromatids.

In mitosis these sisters separate, travel to opposite sides of the cell, a new nucleus and cell wall are made and the cells separate. You end up with a clone of the original cell.

In meiosis this is where it starts being different. During Prophase I your Mom and Dad strands in each sister chromatid swap some of their homologous genes with each other (like the eye color gene from Mom swaps with the eye color gene from Dad) so that the DNA is now not a clone of either parents’ single strand, each strand is now unique. How many and which genes swap is mostly random, iirc, although it’s not a huge percentage.

The rest of the process you can get from the links.

One consequence of this is that, instead of each egg/sperm being either 100% from Dad or 100% from Mom, each of your gametes will be a random recombination of Mom and Dad’s contribution to your genome. Another consequence is that there won’t, generally, be exactly 25% of a child’s genome from each grandparent (remember your parents got exactly 50% from their parents, too). That can vary, roughly, from 20%-30% from each grandparent, depending on how much crossing over there was during Prophase I.

This is a the major contributor to why offspring have completely unique, though still related, genomes and why sexual reproduction usually produces more variety in a population.