Every planet and solar system with life changes when the lifeforms of the planet reaches a certain criteria or planet harnesses lifeforms for certain amount of time. Evolution is the one of the main law of the universe. Every object or being whether they are celestial bodies or a small living being can evolve if they can fulfill the criteria set by universe.
Being in one of the backward places on universe, earth and solar system had to harbour sentient life for certain time to evolve which is different for every planet and solar system. Earth and solar system are small while comparing other planets and solar system. So, it could evolve quickly comparing to other worlds(solar system or in some case plane). Earth started it's evolution just after Sam's death. If it was coincidence or not only god knows.
Just after the Sam's death strange thing started happening all over the earth. Next day which seemed like normal day like before began with strange news on TVs and radios. The temperature on deserts and near volcano sky rocketed. Countries immediately began to evacuate their citizens who lived near volcanic area. As for the people on desert it was not as high as in volcano so they could sustain for few days. Scientists weren't able to tell anything. Next day was even stranger the temperature of desert became unsustainable for human life. The citizens who were near deserts were evacuated. As for the citizens living on deserts they could only save few. How can han survive if temperature rises up to 65 degree in single night and reaches 75 in day. The desert countries had it's worse they were ruined in only two days. Then another news from arctic and antarctic region came. The temperature of these region suddenly dropped by whole 15 degree. Temperature dropping by 15 degrees in every tundra, arctic and Antarctic region wasn't anything to scoff. Many electronic device began to disfunction and scientists also started to get abnormal data from satellites and research institutes.
Within the same week the satellite on orbit began to become unstable. Electronic device around the world weren't function well. Finally after analysing the data over the week from various sources scientists prepared the report of strange happenings which shocked the whole world. The report said that slowly the mass, size and even the magnetic field of earth was increasing and it was the cause of all the strange happening. It wasn't all the thing that shocked even the otaku's was that size and other features of whole solar system was increasing. Public couldn't believe the report. Some began to say it was curse of god, some said it was because of alien invasion and so on.
The second week was the start of nightmare. All the satellites including International space station crashed on earth surface due to increase in gravity and change in earth's magnetic field. Imagine if 4550 satellites suddenly crashed on earth surface how much casualties it can cause. But this wasn't the cause of nightmare. Even the strange temperature fluctuation which has caused deserts and any area which was below zero degree completely unhabitable cannot compare with what was happening on second week. All volcanoes were erupting, strong tides were occurring in ocean but what came with tide became the nightmare of people which every up coming generation of human will not forget. On the second week people began to notice that the height of trees had increased. The trees were more thicker than before. Some tree's leaf's size and shape changed. The medical herbs had their medical property strengthen. Some poisonous plant could cause death just by touching it. The dogs and cats which were under some kind of hibernation for a week suddenly woke up and started to attack their owners. They attacked every creature they saw except of their own kind. The cats and dogs which were favorite animal of many people caused massacre. The animals on forests like amazon and in grassland like savannah all went through mutation. Some became bigger, some became faster and some animals in deserts and volcanic area could even breath fire. The animals of seas and ocean could manipulate water on their will. The cities nearest the forest were attacked and captured. Guns had no effect on them only strong booms and guns with armor penetrating bullets could kill them. But, where will the country prioritize when all cities near forest are attacked on same time. What caused them more headache was that some animals who were deeper into the forest haven't woken up yet. The costal cities suffered the worst. All kinds of sea creatures came on their own group and started to attack all the human they saw. They even had more harmony then the land animals. All kinds of prehistoric aquatic animals could be seen. They will come to land attack till they can then return to ocean and again attack humans. It could be clearly seen a intelligent animal was controlling them. Humans had to use their trump card(nuclear weapon) against these creatures to survive.
After suffering all the pain and destruction caused due to different factors all humans came together and established base cities. Small countries were already eliminated. Only few big and united countries could survive the disaster. Human suffered countless casualties. As for economic and infrastructural damage one could only sigh. The base cities were made with the use of latest technology of humans it had great defense but what protected them wasn't any machines or artillery, the base city was protected by humans. When animals were going through mutation some humans also started to get abnormal strength. On first week they only had strength to defeat a normal rhino if any remained. But starting from second week their strength started to rise rapidly. Only they didn't had their strength increased all of the humans strength was rising but only few had rapid rise in strength.
They slowly managed to protect the base and push away the beasts from base cities.
The strongest among the humans managed to establish order once again but sea was still dangerous. No one dared to venture into forest and seas. Beasts horde used to attack the base city time and time again but strong beasts were still inside forest. The strong beasts have to fight among themselves to become king of the jungle. So, they were keeping themselves in check. As for the small beasts horde it was only warning towards human to forget about the beasts territory. After few years of peace human managed to develop new weapons and armors for those strongest humans. It increased odds towards human a little. But, the strongest humans couldn't survive for long time. The faster they gained the strength, the faster they died. The humans didn't lose anything as they gained key for their survival and evolution.
When the strongest humans were in their peak they notices that their body was absorbing something and strengthing itself. When they worked together with the strongest brains of human they managed to discover Qi which turned new leaf to human evolution. After countless trial and experiment they finally managed to create a method to absorb Qi. After developing cultivation technique all humans were made to cultivate and increase their strength. Slowly human civilization entered into new phase, phase of cultivation and technology. Many genius were born, many legends were created, the crude cultivation technique was modified and developed which they kept to themselves and new era of humans began on earth. Lords of forests were still the taboo which shouldn't be touched. Still, the humans survived and prospered in the end.
Earth and solar system's evolution took ten years to finish. The size of earth and solar system including sun and other planets increased by five times. The mass of earth increased by 50 times and gravity increased by two times. Other planets and sun also had its mass and gravity increased in similar proportion but solar system remained the same. Position of planet and it's satellites didn't changed but distance increased which was proportional to previous solar system.
When everything was over scientists all over the world conducted research. When research was over they were shocked. The research was like bomb to the humans. According to the research only five hundred thousand people should have survived while fifty million humans were alive now. You may think fifty million is still big but fifty million out of seven billion was considered a major disaster. Now, the research was showing ninety nine among hundred of them should have died. Why wouldn't it frighten them? They checked the report again and again but the result was same. Putting these depression things aside humans stabilized human society again, within three decades everything except forest and oceans was like before. Internet was available once again. After five decades humans developed laser technology and equipped it in satellite. These lasers could be said as almost no use. It could easily kill rank 1 and 2 beasts,middle to heavily injure rank 3 beast but had almost no effect on rank 4. When human started to massacre beasts using laser. A beam came from the Pacific ocean and destroyed all the satellites that fired laser. Humans were sure now they were spared. The beasts didn't wanted the humans to be extinct. So they were alive today. This alarmed the scientists but it was kept among the higher ups.
The strength of humans and beasts kept continuously increasing with time. Technology of humans also had major breakthrough.
Now, that Sam is on Earth again we can only wait and see how he faces trials and tempers himself in many life and death battle.