Starting from Robinson Crusoe

Without a container, boiling water solely by using puddles and heated stones is time-consuming and laborious.

During the wait, Chen Zhou had to constantly use a long wooden stick to remove cooled stones and then add new ones.

Paul, meanwhile, held a Wooden Spear and squatted by the river, spearing fish.

Freshwater fish rarely have poison; for fish like yellow catfish, tilapia, and bowfin which have poisonous spines on their backs, while catfish have toxic eggs and internal organs besides their spines. Globefish, which are entirely poisonous, are basically the only kind.

Although neither of them were familiar with prehistoric fish species, by observing their physical traits, they could deduce the ancestral lineage of modern fish types and thereby avoid eating poisonous parts—

While on the island consuming fish and shrimp, due to unfamiliarity with seafood and lack of biological knowledge, Chen Zhou remained exceptionally cautious, even breeding a batch of mice specifically for poison testing.

Now, his experience was much richer; at least he knew to avoid spines, internal organs, and fish eggs, which might be poisonous. By not consuming these parts and heating the fish meat a bit, the high temperature would decompose any toxic substances within the fish, making it safe to eat.

Cold regions not only featured large-sized animals, but even the fish in the rivers were unusually plump.

They had no knowledge of the Long Spear; seeing shadows moving over the river surface, they mistook them for insects or birds that had accidentally fallen into the water and rushed over, only to be skewered by Paul’s spear.

...

Until Paul caught five fish over 30cm long, the water in the puddle hadn’t even boiled, only becoming quite warm, feeling around 80 degrees.

After gathering some more firewood and adding fuel to the campfire, Chen Zhou and Paul began processing the caught fish.

A single Military Saber was not enough for two tasks; Paul pressed the fish onto stones taken from the pit to remove the guts and scrape the scales, Chen Zhou’s approach was more straightforward—

He directly peeled off the fish skin, which although losing some fat, solved the scale problem once and for all.

After processing the exterior of the fish, they removed the fish head and tail, then cut the middle into chunks that could be skewered with tree branches, hanging them over the campfire for slow roasting.

The fish was high in fat content, and once cooked, it emitted an enticing aroma. The rivers in the Prehistoric World had never been polluted by modern industry, so the cooked fish had no strange gasoline or plastic taste.

Though lacking seasoning, the taste was very bland, yet the flavor and texture surpassed any modern dish.

...

It wasn’t until they finished eating the five large fish that the water in the pit finally boiled.

Picking a few large grass leaves by the river and curling them into tubes, taking advantage of the hot water, Chen Zhou and Paul drank most of the water from the pit, then opened the fish bladder and filled it with the remaining water, sealing it with thin threads.

Next, since they needed to walk a long distance, possibly without finding a water source, the hard-boiled water couldn’t be wasted.

If he hadn’t forgotten to save the Cave Hyena bladder when he disassembled it last night, Chen Zhou might have used the Cave Hyena bladder as a water container.

After their meal, Paul again sterilized his wounds by the river, while Chen Zhou selected suitable stones to craft his Stone Hammer.

When binding stone to a wooden stick using the river willow, Chen Zhou didn’t forget to bundle some flexible willow branches—

On the road, he could weave a makeshift guard for Paul as they moved forward, even if it couldn’t form a seamless armor, a thin layer of simple protective net could still block most injuries.

If Paul had had a vine-made guard around his waist last night during the Cave Hyena attack, he might not have been injured, nor have used precious alcohol for sterilization.

...

Once Paul dressed again, Chen Zhou’s Stone Hammer was complete.

Because the willow was untreated, its flexibility was insufficient, so in making the Stone Hammer, he didn’t choose excessively heavy stones to avoid increasing the probability of willow breakage, hence shortening its lifespan.

The entire top of the Stone Hammer weighed about 5 jin, with a short handle barely enough for Chen Zhou to tuck it at his waist, ready to strike enemies anytime, coupled with a versatile Wooden Spear, which, along with his exceptional physique, could usually fend off general beasts.

...

Originally intending to move forward, they were hindered by a big river without tools for crossing, and lacking the time and energy to fell trees, Chen Zhou and Paul had to choose between swimming across the river or exploring on this side.

Looking upstream along the water flow, they saw the terrain rising in the distance, a towering mountain surrounded by sparse pine forests, with snow covering the peak, resembling Changbai Mountain.

The river’s water wasn’t swift, just very icy. If alone, Chen Zhou could swim across.

Yet Paul hadn’t recovered from his former injury, concerned his wounds might get infected when touched by water if swimming across, Chen Zhou decided to remain cautious and walk upstream along the riverbank, hoping to find a narrower river passage they might cross without getting wet.

His confidence in finding a narrower spot upstream stemmed from this river seemingly formed by melted snow converging into streams from all directions to its source, the closer to the source, the less converged the streams, thus the smaller the water volume.

Though it’s easier said than done, starting from here to trace the source, they might not reach it even after dozens or hundreds of kilometers.