First we need to understand "day" in Hebrew means different times, it's called "yown". Genesis 2;1-4, compare Genesis 1:1 with Exodus 20:11 and Isaiah 48:13. Therefore, in order to understand the ticking of time depends on the point of view of God and the human observer and the conditions in nature and simultaneous times in different places of the universe, you need to read the Hebrew explanation with the physicist and theologist who wrote from Jerusalem, Gerald Schroeder, Ph.D., his book is "Genesis and the Big Bang".
Hence, the "day" they started to die was according to the circumstances of their formation (I'm not saying "creation" cos Hebrew is specific in the case of Adam & Eve "formation" from something already existing, different from "barah" which means "create", compare with Genesis 1:26; 2:7, 18, 19, 22).
When the couple had access to the fruit of knowledge they were stopped to have access to the OTHER TREE, the tree of life. So, since that day in both ways, in the perspective of God during thousands of years and the very day that they sinned, there was a whole metamorphosis in their biological system. The access of the tree of knowledge meant a sort of hallucinogic "spiritual" contact with the deceiver (2 Corinthians 11:3), the corruption of Eve's mind probably was something linked to electrochemical frequences (light) directly in the brain (2 Corinthians 11:14), so Samael (Satan) after had sex with Eve and that was the sexual comerce or sin as I have explained in this forum.The chemical structure of serotonine and melatonine or endorfines linked in a key-lock sincronism with wahtever hallucinogenic "tree" allowed the contact with the spiritual realm of the cherub (Ezekiel 28):
www.jornalinfinito.com.br/series.asp?cod=81
www.jornalinfinito.com.br/series.asp?cod=80
They actually became gods and their "eyes" (3rd eye, pituitary gland, melatonine linked to longevity as it's said was demonstrated with experiences with mice) were opened. Genesis 3:7. That text proves Satan didn't lie (3:5). In fact even the plural "god" acknowledged Adam and Eve became like them effectively knowing good and evil (3:22). So the procedure was expelled them from the greenhouse genetic laboratory experience called Eden cos otherwise THEY COULD EFFECTIVELY TAKEN THE OTHER TREE FRUIT, THE EVERLASTING LIFE (3:22, 23).
www.sitchin.com/adam.htm
www.sitchin.com/images/adam1.jpg
www.s8int.com/adamsrib.html
www.sitchin.com/genetics.htm
www.sitchin.com/primate.htm
www.sitchin.com
In the last one, please check the last part.
It's no surprise the more generations advance on time our bodies are accumulating what is called "genetic junk", 3% already of DNA. That is acacaca...adenine-citosine ....repetition rather than adenine-timine, citosine-guanine.... We adquired the intelligence of the gods but we lost the longevity of them cos in their realms one single "year" means more than 3200 Earthly "years". Hence, Sitchin had to explain how come the analysis of the text of Psalms saying part of a "day" means 1000 years to "god" is important in this issue. After all the system we have to measure days, hours, months, week, year, constelations doesn't come from Greece but ancient Sumerian, Maya, etc, ..knowledge. Even the 7th day of resting was kown before Jews in Sumerian "bars". The Annunaki gods, of course, rested in the 7th "bar".