Combining Organic Humans with Artificial Humans seems like a necessary step in Human Development. There are several reasons for this.
1. Organic Humans forget their Identities with Time. Brain Cells get replaced through Neurogenesis slowly, with a completion time of 50 years.
Human Immortality isn't going to function properly until that aspect is at least mitigated.
The Artificial Human side of the Immortal Human exists partially to be the bridge that allows for cheating the systems that cause Organic Humans to degrade, such as the Memory and Identity Problems.
Once the Full Maturity of an Organic Human Identity is detected by the Artificial Human Side, it is locked in by Redundancy Backup Systems that Resynchronize, Reharmonize and Recalibrate the Human Identity when it degrades by a Maximum of 1%.
This is one reason why the Artificial Side must also be Sentient for Self-Operation. That degradation causes Acute Pain that requires Immediate Attention. "The Black Box" of the Human Mind is tied to this, because the Organic Human shouldn't have access to matters of Physical Regulation, for the same reasons we don't have access to other matters of the Body that act autonomously as Animal Instinct. A good reason for this pain is the comfort and complacency through which the Mature Human Mind degrades in the Aging Process starting with Age 26.
That is the Full Maturity of the Body, but the Mind takes until around Age 40. Maturity has to have some balance between some degradation of the Body when approaching the Maturity of the Mind. It would be ideal to have the Peak Physical Condition of Age 26 with the Mental Maturity of Age 40, and that Problem will be Data-Mined by the Artificial Human Side to slowly optimize the Organic Human through reading Biometrics, Processing Logic, and altering Biometrics as Feedback. If this system is not working to standards, it will hurt, and the Organic Human will take Simple Actions to Troubleshoot a Frozen or Slow System.
When Maturity has peaked in a balanced way, the Eyes of the Human will change color, and glow with bioluminescence spliced into the DNA as copy pasted from the DNA of Deep Ocean Aquatic Life that have bioluminescence as part of their bodies. When the System's numbers and efficiency are off by 1%, there will be a pain in the body, and the glow in the eyes will be shut down until physical optimization is restored.
This is for Personal and Social Reasons. You will notice. Your friends and family will notice. People on the street will notice.
"Mommy, why did the lights go out?"
"Oh my God. Larry, call the Police. Jerry is broken. Susie, it's ok. Let's go back inside."
(Under Construction - More Reasons later)