At 18 days theres a heartbeat , at 5 weeks brain activity and a spinal cord. Science has 4 requirements to be "scientifically alive"
- Have its own individual Deoxyribonucleic Acid (DNA).
- Extract energy (food etc.) from its surrounding to convert it into energy to sustain itself.
- Sense changes in surrounding and respond to those changes.
- Be able to reproduce.
The embryo ( human ) can meet all of these requirements.