Summary
Many hostile creatures are found across the map and if you're not careful they'll attack until you're no longer able to. All four types of hostile creatures drop remains when you've put them to sleep and these remains can be researched in the MAM under Alien Megafauna.
Initial Research
The first stage requires just one of either Hog, Hatcher, Stinger or Spitter remains. Once you've unlocked this stage you will be able to craft Alien Protein from remains at the Craft Bench or in a Constructor.
Bio-Organic Properties
You'll need to craft 5 Alien Protein to unlock the Bio-Organic Properties research. When completed you'll be able to craft the Alien DNA Capsule at the Craft bench or in a Constructor along with the ability to turn Alien Protein into Biomass, very useful early game when using Biomass Burners for power.
Protein Inhaler
Multiple research branches are now available starting with the Protein Inhaler which requires 2 x Alien Protein, 20 x Beryl Nut and 50 x Rotors. Once unlocked you'll be able to craft a Medicinal Inhaler at the Equipment Workshop. The Medicinal Inhaler will restore your health to full, very helpful for when you're battling it out with Alien Megafauna or recovering from fall damage.
Early game you can obtain parts like rotors at drop pod crash sites found on the ground, this way you don't have to wait until you've unlocked these technology milestones in the HUB.
Structural Analysis
Researching the Structural Analysis branch requires 5 x Alien DNA Capsules and 100 x Iron Rod. This then reveals The Rebar Gun which requires 25 x Rotors, 50 x Reinforced Iron Plate and 500 Screws to research. Once researched you will be able to craft a Rebar Gun at the Equipment Workshop along with the required ammunition, Iron Rebar. Other types of Rebar ammunition can be unlocked under the Caterium, Quartz and Sulfur research branches of the MAM. The Rebar Gun is a very effective early game weapon, hostile creatures can be taken down from a distance allowing exploration to become easier and more accessible.
Inflated Pocket Dimension
Inflated Pocket Dimension requires 3 x Alien Protein and 1000 cable to research, once unlocked an additional 6 inventory slots will be opened up for the Pioneer.
Expanded Toolbelt
The Expanded Toolbelt can now be researched requiring 5 Alien DNA Capsule and 500 x Steel Beams. This add an additional hand slot for the Pioneer, allowing one more item to be carried and not consume an inventory slot.
Hostile Organism Detection
Last but not least the Hostile Organism Detection can be researched requiring 10 x Alien DNA Capsule, 5 x Crystal Oscillator and 5 x High-Speed Connectors. This will add Enemies to the Object Scanner, allowing you to locate them in your immediate area. However I honestly think this is not a worthwhile feature of the game, I've never used this myself.
All of the hostiles in the game come in several variants, each one having more health points and different attack modes which could involve hurling rocks or fireballs, producing poisonous gas or exposing you to radiation damage. In particular the Hatcher pods eject flying crabs when they detect your presence, however this can be avoided by crouch walking up to the pod and attacking at close range, even the basic Xeno-Zapper will suffice.